Massachusetts Form ST-6 is the Certificate of Payment of Sales or Use Tax for Boat, Recreation or Snow Vehicle that every Massachusetts buyer of a boat, off-highway recreation vehicle, or snowmobile must file with the Massachusetts Department of Revenue within 20 days of the sale or the date the item is first brought into the state. The form is filed and paid through MassTaxConnect, and the certificate it generates is what the Environmental Police, Registry of Motor Vehicles, and harbormasters require before they will register or title your vessel or vehicle.
If you skip ST-6, you cannot legally register the boat, OHV, or snowmobile, and the DOR can assess the unpaid 6.25% tax plus interest and a late-file penalty of 1% per month up to 25% under the rules in 830 CMR 62C.16.2. The DOR processes tens of thousands of ST-6 submissions every year, and the most common rejection reason is a mismatch between the hull or vehicle identification number on the bill of sale and the number entered on the form.
In this article you will learn:
- 🛥️ Who must file ST-6 and who instead files the exemption form, ST-6E.
- 📝 How to fill in every box of Part A (dealer sale) and Part B (private sale) line by line.
- 💵 How to compute the tax, trade-in adjustment, and any penalties or interest you owe.
- 🧾 Three full walkthroughs for a private boat sale, a dealer snowmobile sale, and an out-of-state OHV brought into Massachusetts.
- ⚠️ The 10 most expensive mistakes filers make and how to avoid each one.
What Form ST-6 Is and Who Must File It
Form ST-6 is the official receipt the Massachusetts Department of Revenue uses to confirm that the 6.25% sales or use tax on a boat, off-highway recreation vehicle (OHV), or snowmobile has been paid. The current revision printed on the form itself is Rev. 3/15, and the PDF on Mass.gov remains the controlling version for paper backup, even though most filers now submit electronically through MassTaxConnect. The statute behind the tax is M.G.L. c. 64H, § 2 for sales tax and c. 64I for use tax on items bought outside the state.
You must file ST-6 if you bought any of the following and intend to use, store, moor, or register it in Massachusetts:
- A boat of any size, including kayaks with motors, sailboats, and personal watercraft.
- A snowmobile, regardless of engine size or where it is ridden.
- An off-highway recreation vehicle such as a dirt bike, ATV, side-by-side, or UTV.
You file ST-6 even when you bought the item from a private party with no dealer involved. In that case the buyer fills out Part B of the form and pays the tax directly. If a registered Massachusetts dealer sold the item, the dealer collects the tax at delivery and completes Part A for you, but the buyer’s signature is still required on the Mass.gov boats and recreational OHV guidance page.
If your purchase qualifies for an exemption, such as a transfer between immediate family members or a sale to a 501(c)(3) holding a Form ST-2 certificate, you file Form ST-6E instead. The exemptions follow the list in M.G.L. c. 64H, § 6. Filing ST-6E is still mandatory because the Environmental Police and harbormasters require either a paid ST-6 certificate or an approved ST-6E before they will issue a registration decal.
Before You Start: Documents and Information You Need
Open the form only after you have gathered every document below, because MassTaxConnect times out after roughly 20 minutes of inactivity and you cannot save a partial ST-6 submission. The system also rejects entries that do not match the bill of sale exactly, so each item on this checklist matters.
- Bill of sale signed by both parties. Without it, you cannot prove the gross sales price entered on Line 1, and the DOR can substitute its own book value under the audit rules in the Mass.gov sales and use tax guide.
- Hull Identification Number (HIN) for boats or Vehicle Identification Number (VIN/serial) for OHVs and snowmobiles. A wrong digit triggers a registration hold at the Massachusetts Environmental Police.
- Make, model, model year, engine size, and length. These four data points must match the title or manufacturer’s statement of origin.
- Date of sale in MM/DD/YYYY format. The 20-day filing clock starts on this date for in-state purchases.
- Date first brought into Massachusetts. This is the trigger date for use tax if the item was bought out of state, per the Massachusetts business use tax page.
- Buyer’s Social Security number or Federal Identification Number. Individuals use SSN; businesses and sole-proprietors filing under an EIN use the FID.
- Seller’s full legal name, address, and FID if a dealer. Missing seller information is the most common reason a private-party submission gets flagged for review.
- Trade-in details if you traded another boat or vehicle. You will need the traded item’s make, model year, and VIN/HIN to claim the deduction on Line 2.
- Manufacturer’s rebate documentation, if any. A rebate from the manufacturer reduces the taxable price on Line 3, but a dealer discount does not.
- City or town of mooring or principal use. This determines the local jurisdiction the DOR reports to and, for boats, drives the excise tax billing by the harbormaster.
- A credit card, debit card, or bank account for payment. MassTaxConnect accepts ACH debit at no cost; cards carry a third-party convenience fee.
Where to Get the Form and How to Access It
The official ST-6 lives on the Mass.gov sales and use tax forms list and on the dedicated Form ST-6 PDF page. The PDF is fillable in Adobe Acrobat, but the DOR no longer accepts paper ST-6 filings except in narrow hardship cases. Almost every filer uses the electronic version on MassTaxConnect, which mirrors the paper form box for box.
To reach the electronic ST-6 you do not need to log in or create a MassTaxConnect account. From the home page, scroll down to the Quick Links column and click File and Pay Boat/Vehicle (ST-6). The system will ask whether you have a confirmation code from a prior session; first-time filers click No and proceed.
You can also find a previously filed ST-6 using the Find a submission link under Quick Links, which the DOR walkthrough video demonstrates step by step. To pull up an old certificate you need the email address you used at filing and the confirmation code from the confirmation page. If you lost the code, the DOR contact center at 617-887-6400 can recover it after verifying your identity.
Always confirm you are using the Rev. 3/15 version of the form, which is the current paper version printed on the Mass.gov ST-6 PDF. Older revisions still circulate on third-party sites such as pdfFiller and the DOR will reject them on audit.
Step-by-Step: How to Fill Out Form ST-6 Line by Line
The form has a header block that everyone completes, a Part A for dealer sales, and a Part B for private-party sales. Complete the header first, then jump to either Part A or Part B based on who sold you the boat, OHV, or snowmobile.
Name of Purchaser/Business
This box asks for the legal name of the person or business that bought the item and will register it. Enter the name in the same form it appears on your driver’s license or your IRS EIN letter, with no nicknames. For a couple titling jointly, enter both names separated by and, for example Maria Lopez and Daniel Lopez.
A specific example: Maria Lopez, who just bought a used Boston Whaler on Cape Cod, types Maria Lopez in the purchaser box. If she had formed an LLC to hold the boat, she would instead enter Lopez Marine LLC.
The most common edge case is a name change after marriage or divorce. Use the name on your current Social Security card, because the DOR cross-checks the SSN against SSA records, and a mismatch will hold up your registration at the Environmental Police.
A common mistake is entering the seller’s name here because the form’s layout suggests two name lines side by side. The direct consequence is that the certificate prints with the seller as the taxpayer, which voids it for registration.
A misconception is that a co-owner can be left off if both will use the boat. If both names appear on the registration, both must appear here, otherwise the harbormaster will refuse to issue the decals.
Federal Identification Number or Social Security Number
The form gives you two number fields side by side, and you fill exactly one. Individuals enter their nine-digit SSN; businesses and sole-proprietors filing under an EIN enter the FID; sole-proprietors who never obtained an EIN use their SSN.
For example, Marcus Chen, a self-employed carpenter buying an ATV for personal weekend riding, enters his SSN, 123-45-6789, even though he has an EIN for his business. The ATV is personal, so personal identification controls.
The edge case is a single-member LLC. The IRS treats it as a disregarded entity, but Massachusetts wants the LLC’s EIN here if the LLC is taking title.
A common mistake is entering both numbers, which causes MassTaxConnect to throw a validation error and lock the page until you clear one. The fix is to refresh and start over.
The misconception is that ITIN holders cannot file. They can, and they enter the ITIN in the SSN field; the system accepts the 9XX format used by the IRS.
Mailing Address, City/Town, State, Zip
This is the address where the DOR will mail any correspondence, audit notice, or refund check. Use a street address you actually receive mail at, not the boat’s mooring address.
A specific example: 47 Beach Plum Lane, Yarmouth, MA 02675 for Maria Lopez. The system validates the ZIP against the city, so a typo in either field rejects the entry.
The edge case is filers with a P.O. Box. The form accepts a P.O. Box, but if you list one, the DOR may also send notices to any street address it has on file from your income tax returns.
The mistake to avoid is using the seller’s address copied from the bill of sale. If a notice goes there, you may never see it, and the resulting failure to respond can escalate to a Notice of Assessment.
The misconception is that the address determines the local tax rate. Massachusetts has a single statewide 6.25% rate, so the address is purely for correspondence and statistical reporting.
Filer Type Boxes: Business, Sole-Proprietor, Individual
You fill in exactly one of these three ovals to tell the DOR what kind of taxpayer you are. The classification controls which identification number is valid and whether the certificate prints in a personal or business name.
For example, Janet Reilly, who runs a tour-boat sole proprietorship, fills Sole-proprietor and enters her EIN. If Janet were buying the boat for family use only, she would fill Individual and enter her SSN.
The edge case is a married couple buying jointly. Both names go on the purchaser line, Individual gets filled in, and one spouse’s SSN goes in the SSN box; the DOR’s system links the second spouse through the joint registration.
The mistake is filling Business when you only have a sole proprietorship. The system will demand a separate corporate FID, and your submission will fail validation.
The misconception is that filing as a Business lowers the tax. The 6.25% rate is the same for every filer type; the box only changes how the certificate is captioned.
Amended Return Oval
Fill this oval only when you are correcting a prior ST-6 filing. The amended return replaces, not supplements, the original.
For example, if Marcus Chen later discovers he forgot to claim a $500 trade-in allowance, he files a new ST-6 with all original information plus the corrected Line 2 entry, and fills the Amended Return oval at the top.
The edge case is amending after the DOR has already issued an assessment. In that case, you should file an Application for Abatement, Form CA-6, instead of an amended ST-6.
The mistake is filing an amended return without including the original confirmation number in the explanation field. Without it, the DOR treats the amended filing as a duplicate and may double-bill the tax.
The misconception is that amendments must be on paper. They go through MassTaxConnect just like original filings.
Dealer Sale Oval and Vehicle Type Selection
Fill in Dealer sale only when a Massachusetts-registered dealer sold the boat or vehicle and is collecting the tax at delivery. Then choose exactly one of Boat, Rec. vehicle, or Snow vehicle.
For example, Marcus buys his Polaris RZR from Cape Cod Powersports, a registered dealer, so he fills Dealer sale and Rec. vehicle.
The edge case is a sale by an out-of-state dealer not registered in Massachusetts. That counts as a private sale for ST-6 purposes; you skip the Dealer sale box and complete Part B yourself.
The mistake is checking Dealer sale when buying from a Craigslist seller because the seller has a business name. The DOR cross-references its registered-dealer list, so the discrepancy will reject the filing.
The misconception is that Rec. vehicle covers street-legal motorcycles. It does not; on-road motorcycles use Form RMV-1 at the Registry of Motor Vehicles.
Make, Model Year, Model Name, Engine Size, Type/Length
These five descriptors must match the title, MSO, or registration card exactly. The DOR uses them to verify the item is the same one being registered.
For example, Maria’s Boston Whaler entry reads Make: Boston Whaler, Model year: 2014, Model name: Montauk 170, Engine size: 90 HP, Type/length: 17 ft center console.
The edge case is a homemade boat with no model name. Enter Homemade and attach the state-issued HIN documentation; the DOR will accept this when paired with a notarized homemade-vessel statement.
The mistake is rounding length to whole feet when the title shows decimals. A 17.4 ft entry on the title typed as 17 ft triggers a manual review.
The misconception is that engine size is optional for sailboats. Auxiliary engine horsepower must still be entered if any motor is installed.
Serial or Vehicle Identification Number
This is the most field-rejected box on the entire form. Enter the HIN for boats (12 characters since 1972) or the VIN/serial for OHVs and snowmobiles, exactly as it appears on the hull or frame.
For example, Maria types BWCE0123A414 with no spaces, dashes, or lowercase letters.
The edge case is a worn or unreadable HIN. Massachusetts will issue a state-assigned HIN through the Environmental Police, and you enter that number here.
The mistake is confusing the letter O with the number 0. HINs after 1984 never contain the letter O, so any O you typed is wrong and must be a zero.
The misconception is that the registration number, like MS 1234 AB, can be substituted for the HIN. The HIN is permanent and federally assigned; the registration number changes.
Date of Sale and Date First Brought Into Massachusetts
Date of sale is the date on the bill of sale, in MM/DD/YYYY format. Date first brought into Massachusetts is required only if you bought the item out of state.
For example, Aisha Patel buys a snowmobile in New Hampshire on 01/05/2026 and trailers it home on 01/07/2026. Both dates go on the form.
The edge case is a boat kept on a trailer in another state and only brought to Massachusetts the following spring. The use-tax clock starts on the date it crosses the state line, not the purchase date.
The mistake is leaving Date first brought into Massachusetts blank for an out-of-state purchase. The DOR’s system flags the use-tax filing as incomplete, and you cannot register without that date.
The misconception is that 6 months out of state exempts the buyer. Under M.G.L. c. 64I, § 7(b), the exemption requires non-resident use of more than 6 months and documentary proof such as out-of-state registration.
City/Town of Boat Mooring, USCG Documentation Number, Name of Vessel, Hailing Port
These four fields apply to boats only. The mooring city is where the boat will spend most of its time on the water. The USCG documentation number is required only for vessels documented federally, generally those over 5 net tons.
For example, Maria’s boat lives at a private mooring in Yarmouth, so she enters Yarmouth as the mooring city and leaves USCG, vessel name, and hailing port blank because her 17 ft Whaler is state-registered, not federally documented.
The edge case is a documented yacht. Owners enter the USCG number, the documented vessel name (e.g., Sea Glass), and the hailing port painted on the transom.
The mistake is leaving the mooring city blank because the boat will be trailered. Even trailered boats must list their primary launch town for the local excise database.
The misconception is that hailing port must be a Massachusetts city. It can be any port the owner chooses, subject to USCG requirements; many Massachusetts boats hail from Boston even when moored elsewhere.
Part A, Line 1: Gross Sales Price
For a dealer sale, this is the price the dealer charged you before any trade-in or rebate, including any dealer-installed options but excluding the trailer. Enter dollars and cents.
For example, Marcus’s RZR was $18,995.00 on the dealer’s bill of sale, so 18995.00 goes on Line 1.
The edge case is a bundled boat-and-trailer price. You must allocate, and the dealer must show the trailer price separately because the trailer is taxed under Form RMV-1, not ST-6.
The mistake is including delivery, prep, or documentation fees in Line 1. These are taxable, so they belong on Line 1, but freight separately stated on the invoice is not. Misclassifying causes either underpayment or overpayment.
The misconception is that a dealer’s advertised discount can be subtracted here. Only manufacturer rebates qualify (Line 3); dealer discounts are simply reflected in a lower Line 1.
Part A, Line 2: Trade-In Allowance
A trade-in of a like item, meaning a boat traded for a boat or an OHV traded for an OHV, reduces the taxable price. Enter the dollar value the dealer credited you on the bill of sale.
For example, Marcus traded a 2018 ATV worth $4,000 toward the RZR, so Line 2 reads 4000.00. He also enters the traded ATV’s make, model year, and VIN in the boxes below Line 2.
The edge case is trading a boat against an OHV. The trade-in must be the same kind of item, so a cross-category trade does not qualify and Line 2 stays at zero.
The mistake is failing to fill in the traded item’s VIN/HIN. Without it, the DOR disallows the trade-in and re-bills the tax on the full Line 1.
The misconception is that a trade-in to a private buyer counts. Only trades to the registered dealer on the same transaction qualify; private-party swaps do not.
Part A, Line 3: Manufacturer’s Rebate
A rebate paid by the manufacturer, not the dealer, is subtracted here. The rebate documentation must come from the OEM.
For example, Polaris offered Marcus a $500 factory rebate. He enters 500.00 on Line 3 and keeps the rebate notice.
The edge case is a combined rebate split between manufacturer and dealer. Only the manufacturer’s portion goes on Line 3.
The mistake is entering a finance-company cash incentive as a manufacturer rebate. Cash incentives from the lender are not rebates and do not reduce the taxable base.
The misconception is that the rebate is non-taxable income. It is excluded from the taxable price on the boat or vehicle, but it does not change the federal income tax treatment of the purchase.
Part A, Line 4: Total Adjustments
Add Line 2 and Line 3 and enter the sum. The form does not auto-calculate on the PDF; MassTaxConnect does.
For example, Marcus’s Line 4 is $4,500.00 (4,000 trade-in + 500 rebate).
The edge case is no trade-in and no rebate, in which case Line 4 is 0.00. Do not leave it blank, as some DOR scanners read blank fields as errors.
The mistake is adding sales-tax credits or out-of-state tax paid on Line 4. Out-of-state tax goes through a different abatement process, not Line 4.
The misconception is that you can add anticipated rebates. Only rebates already received or contractually guaranteed at the point of sale belong on Line 3 and therefore in the Line 4 sum.
Part A, Line 5: Taxable Sales Price
Subtract Line 4 from Line 1. This is the figure the 6.25% rate is applied to.
For example, Marcus’s Line 5 is $14,495.00 (18,995 − 4,500).
The edge case is a negative result, which is impossible if Line 1 was correct. A negative Line 5 means an arithmetic error somewhere upstream.
The mistake is rounding to whole dollars. The form requires cents, and the DOR’s automated audit looks for exact matches with bills of sale.
The misconception is that the taxable sales price equals the fair market value. It does not; it equals the contract price after adjustments, even if that is below FMV.
Part A, Line 6: Sales Tax Collected
Multiply Line 5 by 0.0625 and enter the result rounded to the nearest cent. This is the dollar figure the dealer must remit to the DOR.
For example, Marcus’s Line 6 is $905.94 (14,495 × 0.0625).
The edge case is fractional cents. Round half up, so 905.9375 becomes 905.94.
The mistake is using an old 5% or 6% rate. The 6.25% rate has been in place since August 1, 2009, per the Sales and Use Tax guide.
The misconception is that local-option meal taxes apply. They do not; boats, OHVs, and snowmobiles carry only the state 6.25% rate.
Part B, Line 1: Gross Sales Price (Private Sale)
For a private-party sale, enter the price the buyer paid the seller. There is no trade-in line in Part B because individuals are not registered dealers.
For example, Maria paid $12,500 cash for the used Whaler, so 12500.00 is her Part B Line 1.
The edge case is a price clearly below market. The DOR may use the NADA or BUC value as a floor unless the buyer attaches photos or a survey showing damage that explains the low price.
The mistake is reporting $1.00 on a parent-to-child transfer to dodge tax. Family transfers are exempt under ST-6E; reporting $1 on ST-6 invites a fraud review.
The misconception is that gift transactions need no filing. They need ST-6E, not ST-6, but a filing is still required.
Part B, Line 2: Sales/Use Tax
Multiply Line 1 by 0.0625. The buyer pays this directly to the DOR.
For example, Maria’s Line 2 is $781.25 (12,500 × 0.0625).
The edge case is paying tax in another state already. You may credit out-of-state tax paid up to the Massachusetts amount; attach proof of payment.
The mistake is forgetting that use tax applies even when the boat was bought from a friend in New Hampshire. Crossing the state line triggers it.
The misconception is that private sales are sales-tax-free. Only the seller is exempt from collecting; the buyer must self-assess and pay.
Part B, Line 3: Penalties and Interest
If you file more than 20 days after the sale or the date the item entered Massachusetts, add a late-file penalty of 1% per month (max 25%), a late-pay penalty of 1% per month (max 25%), and interest at the federal short-term rate plus 4 percentage points under 830 CMR 62C.16.2.
For example, if Maria files 90 days late, she owes roughly 3% late-file + 3% late-pay + interest on the $781.25.
The edge case is reasonable cause. The DOR can waive penalties (not interest) if the filer shows hospitalization, natural disaster, or similar hardship.
The mistake is rounding partial months down. Any fraction of a month counts as a full month.
The misconception is that interest stops once you file. Interest accrues until the tax is paid, not just filed.
Part B, Line 4: Total
Add Lines 2 and 3 and pay this amount. MassTaxConnect computes it automatically.
For example, on-time, Maria pays $781.25.
The edge case is paying by check on a paper filing. Mail to Massachusetts DOR, PO Box 7066, Boston, MA 02204 with the form stapled at the indicated location.
The mistake is paying the seller and assuming they will remit. In a private sale, the seller has no remittance duty.
The misconception is that the bank account on file with prior tax returns is auto-charged. ST-6 requires fresh payment information each filing.
Declaration, Signatures, and Dates
Both buyer and seller must sign and date the form under the penalties of perjury declaration. The buyer’s signature is the legally operative one for filing; the seller’s signature confirms the price.
For example, Maria signs as purchaser on 03/14/2026; the seller signs the same day.
The edge case is a remote closing. Electronic signatures through the MassTaxConnect submission satisfy the requirement.
The mistake is signing before all numeric fields are complete. The declaration covers the entire form, so any later edit voids the signature.
The misconception is that a notary is required. ST-6 does not require notarization; the perjury declaration is sufficient.
Three Filled-Out Examples Using Real Scenarios
Scenario 1: Maria Lopez Buys a Used Boat from a Neighbor
Maria pays $12,500 for a 2014 Boston Whaler Montauk 170 from a private seller in Yarmouth on 03/14/2026.
| Form Section | What Maria Enters |
|---|---|
| Name of purchaser | Maria Lopez |
| SSN | 123-45-6789 |
| Filer type | Individual |
| Item type | Boat |
| Make / model / year | Boston Whaler / Montauk 170 / 2014 |
| HIN | BWCE0123A414 |
| Date of sale | 03/14/2026 |
| Mooring city | Yarmouth |
| Part B Line 1 (gross price) | $12,500.00 |
| Part B Line 2 (tax) | $781.25 |
| Part B Line 4 (total due) | $781.25 |
Scenario 2: Marcus Chen Buys a Side-by-Side from a Dealer with a Trade-In
Marcus buys a 2026 Polaris RZR for $18,995 from Cape Cod Powersports on 04/02/2026, trading a 2018 ATV worth $4,000 and using a $500 factory rebate.
| Form Section | What Marcus Enters |
|---|---|
| Name of purchaser | Marcus Chen |
| SSN | 234-56-7890 |
| Filer type | Individual |
| Dealer sale oval | Filled |
| Item type | Rec. vehicle |
| VIN | 3NSVDE99XPK123456 |
| Part A Line 1 (gross) | $18,995.00 |
| Part A Line 2 (trade-in) | $4,000.00 |
| Part A Line 3 (rebate) | $500.00 |
| Part A Line 5 (taxable) | $14,495.00 |
| Part A Line 6 (tax) | $905.94 |
Scenario 3: Aisha Patel Brings a New Hampshire Snowmobile into Massachusetts
Aisha buys a 2025 Ski-Doo Renegade for $9,800 in New Hampshire on 01/05/2026, then trailers it to Berkshire County on 01/07/2026.
| Form Section | What Aisha Enters |
|---|---|
| Name of purchaser | Aisha Patel |
| SSN | 345-67-8901 |
| Filer type | Individual |
| Item type | Snow vehicle |
| Make / model / year | Ski-Doo / Renegade / 2025 |
| Serial number | 2BPSCEKB5NV000123 |
| Date of sale | 01/05/2026 |
| Date first brought into MA | 01/07/2026 |
| Part B Line 1 (gross) | $9,800.00 |
| Part B Line 2 (use tax) | $612.50 |
| Part B Line 4 (total due) | $612.50 |
How to File the Completed Form
The fastest way to file is through the MassTaxConnect ST-6 portal, which the DOR’s boats and recreational OHVs page directs everyone to. There is no fee to use the portal, and it produces a printable certificate within seconds of payment.
For online filing, click File and Pay Boat/Vehicle (ST-6) on the MassTaxConnect home page, enter the data from your bill of sale, and pay by ACH debit (free) or credit/debit card (third-party convenience fee around 2.35%). Processing is essentially instantaneous; print the confirmation page and the certificate that it links to. Keep both for life because the harbormaster, RMV, and Environmental Police can request them at any future registration renewal.
For paper filing in hardship cases, mail the completed PDF with a check to Massachusetts Department of Revenue, PO Box 7066, Boston, MA 02204, payable to Commonwealth of Massachusetts. Processing takes 4 to 6 weeks, and you cannot register the boat or vehicle until the certificate returns.
In-person filing is available at the DOR’s Boston walk-in center at 200 Arlington Street, Chelsea, MA 02150, but appointments are limited and same-day certificates are not guaranteed. Fax filing was discontinued in 2019.
Whatever channel you choose, the proof-of-filing you must keep is the MassTaxConnect confirmation code along with the printable ST-6 certificate. Without it, you cannot use the Find a submission lookup later.
What Happens After You File
Once your payment clears, MassTaxConnect generates a numbered certificate confirming the tax has been paid. You print it and bring it, along with the original bill of sale and your photo ID, to the Massachusetts Environmental Police registration office for boats and OHVs, or to your local Registry of Deeds in some snowmobile cases.
The DOR matches your filing against dealer reports and, for private sales, may compare the reported price to industry guides. If the system flags a discrepancy, you receive a Notice of Intent to Assess by mail at the address you entered on the form. You then have 30 days to respond with documentation supporting the price you reported.
If everything matches, no further notice is sent and the certificate stays valid for the life of the boat or vehicle. Future owners who buy the same item will file their own ST-6, and your certificate becomes part of the chain of title that the DOR keeps on file.
If you discover an error after filing, you can submit an amended ST-6 through MassTaxConnect or, for assessments already issued, file Form CA-6 Application for Abatement within three years of the date the original tax was due.
Mistakes to Avoid When Filling Out the Form
- Mistyping the HIN or VIN. The Environmental Police will not register the boat or vehicle until the certificate matches the hull or frame.
- Reporting $1 on a family transfer. Family transfers belong on ST-6E; the $1 trick on ST-6 invites a fraud review.
- Including the trailer price on Line 1. Trailers are taxed at the RMV, not on ST-6, so including them double-taxes you.
- Leaving Date first brought into Massachusetts blank for out-of-state purchases. The use-tax filing fails validation without it.
- Filing under the seller’s name. The certificate prints in the wrong name and is useless for registration.
- Using a P.O. Box that you do not check. DOR notices may arrive there and go unanswered, escalating to assessment.
- Forgetting to fill in the trade-in’s VIN/HIN below Line 2. The DOR disallows the trade-in deduction and re-bills the tax.
- Filing more than 20 days after the sale. Penalties accrue at 1% per month on both filing and payment, capped at 25% each.
- Using the 5% rate from pre-2009 examples online. The current rate is 6.25% under the Sales and Use Tax guide.
- Skipping the form because the seller said they would handle it. Private sellers cannot remit; only registered dealers can.
- Treating a dealer discount as a manufacturer rebate. Only OEM rebates reduce Line 5; dealer discounts are reflected in Line 1.
- Closing the browser before printing the certificate. Recovering it requires the confirmation code, and replacement requires a 617-887-6400 call.
Do’s and Don’ts
- Do file within 20 days of the sale or the date the item entered Massachusetts to avoid penalties under 830 CMR 62C.16.2.
- Do keep the confirmation page and PDF certificate forever, because every future registration renewal can request proof.
- Do match every entry to your bill of sale exactly, because mismatches trigger manual review.
- Do use the official Mass.gov ST-6 PDF only, not third-party copies that may be outdated.
- Do fill the Amended Return oval if you correct a prior filing, so the DOR replaces rather than duplicates the record.
- Do call 617-887-6400 promptly if your confirmation code is lost, because waiting risks losing access entirely.
- Don’t assume a private seller will remit the tax for you, because they have no authority to do so.
- Don’t include the trailer in Line 1; the trailer goes on the RMV-1 instead.
- Don’t report a sale price below true value without documentation, because the DOR can substitute book value.
- Don’t sign the form before completing every numeric field, because later edits void the perjury declaration.
- Don’t forget the Date first brought into Massachusetts on out-of-state buys, because it sets the use-tax start date.
- Don’t file ST-6 if your purchase qualifies for an exemption; file ST-6E instead.
Pros and Cons of Filing on Your Own vs. With Help
| Pros of Self-Filing | Cons of Self-Filing |
|---|---|
| Free aside from optional 2.35% card fee | You bear full responsibility for HIN/VIN accuracy |
| Instant certificate from MassTaxConnect | No professional to spot trade-in or rebate errors |
| Direct control over data entry | Easy to miss the 20-day filing window |
| No third-party data sharing | Confusing if buying from out of state |
| You learn the form for future purchases | DOR notices come straight to you with no buffer |
A dealer or marine broker who files for you charges roughly $50 to $150 but absorbs the data-entry risk and often catches missing trade-in or rebate documentation. A CPA or tax attorney is overkill for a routine ST-6 but worth hiring if the purchase is a high-value documented yacht, an aircraft purchased in another state, or a transaction that may qualify for a complex exemption under M.G.L. c. 64H, § 6.
FAQs
Is ST-6 required for kayaks and canoes without motors?
No. Massachusetts only taxes and registers boats with motors or sails large enough to require registration; an unpowered kayak or canoe is exempt and needs no ST-6 filing.
Do I file ST-6 if I bought my boat in Rhode Island?
Yes. Use tax applies to any boat brought into Massachusetts within 6 months of out-of-state purchase, and you file ST-6 Part B with the date the boat entered Massachusetts.
Can a parent transfer a snowmobile to a child without paying tax?
Yes. Family transfers between spouse, parent, child, or sibling are exempt, but you must file Form ST-6E instead of ST-6 to claim it.
Do I write my SSN or my LLC’s EIN in the ID box?
Yes, use whichever entity is taking title; if the LLC is on the registration, use the EIN, but if you personally own the boat, use your SSN.
Is the trailer included in Line 1 of Part A?
No. Trailers are taxed separately at the Registry of Motor Vehicles using Form RMV-1, and including the trailer on ST-6 Line 1 will double-tax you.
Do I enter the registration number or the HIN in the serial box?
No, never the registration number; enter the 12-character Hull Identification Number permanently affixed to the transom or the VIN/serial on the OHV or snowmobile frame.
Can I claim a credit for sales tax I already paid in another state?
Yes. Massachusetts allows a credit up to the Massachusetts tax due, attached as a receipt to the Part B filing under the rules in the Sales and Use Tax guide.
Is a dealer discount the same as a manufacturer’s rebate on Line 3?
No. Only manufacturer rebates go on Line 3; dealer discounts are simply reflected in a lower Line 1 gross price.
Do I need a notary on the signature block?
No. ST-6 uses a perjury declaration, not notarization, so neither buyer nor seller needs a notary stamp.
Can I file ST-6 on paper instead of MassTaxConnect?
No, not in the ordinary case; the DOR requires electronic filing through MassTaxConnect and accepts paper only in narrow hardship situations.
Is the 6.25% rate the same for boats, OHVs, and snowmobiles?
Yes. Massachusetts charges a single 6.25% sales or use tax on all three categories, with no local-option add-on for these items.
Do I owe a penalty if I file ST-6 on day 21 after the sale?
Yes. Any portion of a month past the 20-day deadline triggers a 1% late-file penalty plus 1% late-pay penalty under 830 CMR 62C.16.2.
Can I recover a lost ST-6 confirmation code?
Yes. Call the DOR contact center at 617-887-6400 option 1, verify your identity, and they will resend the code so you can use Find a submission on MassTaxConnect.
Related reading
- How to Fill Out Massachusetts Form ST-12 (w/Examples) + FAQs
- How to Fill Out Massachusetts Form ST-2 (w/Examples) + FAQs
- How to Fill Out Massachusetts Form ST-4 (w/Examples) + FAQs
- How to Fill Out Massachusetts Form ST-5 (w/Examples) + FAQs
- How to Fill Out Massachusetts Form ST-9 (w/Examples) + FAQs
- How to Fill Out Massachusetts Form ST-9A (w/Examples) + FAQs
- How to Fill Out Massachusetts Form 1 (w/Examples) + FAQs