How to Fill Out Maryland Form 502UP (w/Examples) + FAQs

Maryland Form 502UP is the Underpayment of Estimated Income Tax by Individuals form that you attach to your Maryland return when you did not pay enough income tax during the year through withholding or estimated payments. You file it with Form 502, 505, or 515 to figure the interest you owe the Comptroller of Maryland for paying too little, too late.

This form matters because Maryland charges interest the moment your tax bill after withholding tops $500 and you did not keep up with the four installment due dates. The 2025 version (revision 09/25, COM/RAD 017) computes interest at 0.9568% per month for due dates before January 1, 2026, and 0.9011% per month after, which works out to a steep annual rate above 11% on the money you held back, as shown in the official 2025 Form 502UP.

Here is what you will learn in this guide:

• 🧾 What every line on Form 502UP asks and exactly how to fill it in.
• 💰 How to use the $500 exception and the safe harbor rules to skip the form entirely.
• 🗓️ How the four installment due dates and interest factors actually work.
• 👥 Three full walkthroughs for a freelancer, a retiree, and an investor.
• ⚠️ The field-level mistakes that cost filers the most money and how to dodge them.

What Form 502UP Is and Who Must File It

Form 502UP is the worksheet the Comptroller of Maryland uses to calculate underpayment interest on estimated income tax. The legal backbone is Section 10-815 of the Tax-General Article, which requires anyone who gets taxable income not subject to Maryland withholding to make estimated payments and file Form PV when that income will develop more than $500 of tax above withholding. Sections 13-602 and 13-702 then add the interest and penalty if you fall short.

You must file Form 502UP if you owe interest for underpaying, or if you want to lower or erase that interest because your income arrived unevenly during the year. The plain-English test is simple: if your tax bill after subtracting Maryland withholding is more than $500, and you did not pay enough on time, this form figures the damage.

A key consequence to understand is what happens when you ignore the requirement. Under COMAR 03.04.01.02, the Comptroller assesses interest on the unpaid tax from the due date until you pay. If you skip the form, the state does not forgive the interest. Instead, Maryland figures it for you and mails a bill, often with less favor than if you had claimed the uneven-income method yourself.

A common misconception is that Maryland charges a flat “penalty” like a parking ticket. In reality, the state frames this almost entirely as interest tied to time and dollars, so the longer and larger your shortfall, the more you owe. This is why early payment, even a few weeks early, shrinks the bill.

One more group should pay attention: self-employed people, retirees taking large distributions, and investors with big capital gains. These filers rarely have enough tax withheld, so they are the most likely to trip the $500 threshold and need this form.

Before You Start: Documents and Information You Need

Filling out Form 502UP goes fast when you gather your numbers first. Each item below feeds a specific line, and a missing piece forces you to guess, which is the top cause of wrong interest amounts.

• Your completed 2025 Form 502 or 505. You pull Line 16, Line 34, and credit lines straight from it; without the finished return, the 502UP numbers have nowhere to come from.
• Your 2024 Form 502 or 505. Line 9a needs your prior-year tax, and a wrong prior-year figure breaks the safe harbor math.
• Records of all 2025 estimated payments. You need the date and amount of each Form PV/502D payment so Line 14 is accurate by quarter.
• All W-2s and 1099s showing Maryland tax withheld. Withholding counts as paid evenly across the year, so these reduce your underpayment.
• A month-by-month income log if your income was uneven. This powers the annualized method on Lines 11 through 15 and can wipe out interest.
• Any 2024 amended-return adjustments. If your 2024 tax was corrected, Line 9a must include the extra tax or your safe harbor is overstated.
• Form 502TP, if you have tax preference items. Line 5 depends on it, and skipping it understates the tax you should have paid.
• Records of nonresident tax paid on your behalf. Tax paid by an S corporation, partnership, or LLC counts on Line 14 and is easy to forget.
• Your filing status and Social Security numbers. The header must match your return exactly, or the form may not be matched to your account.

If any item is missing, stop and find it before you write a single number. Guessing on the prior-year tax or a payment date is the difference between owing $40 and owing $400.

Where to Get the Form and How to Access It

The safest source is the Comptroller of Maryland, which posts the current 502UP each year. You can download the 2025 Form 502UP PDF directly, and the revision stamp 09/25 in the corner confirms you have the right version. Always check that stamp, because an old form uses outdated interest factors and produces the wrong number.

You can also reach the form through the Comptroller’s income tax forms page, which lists 502UP alongside Form 502, 505, and 515. If you prefer software, most major tax programs generate 502UP for you, though some struggle with the four annualized columns, so review the output by hand.

One important access note: Maryland’s free iFile system does not support Form 502UP for tax year 2025. If you file through iFile and owe more than $500, the system will flag the underpayment, but you cannot complete the 502UP inside it. You either let the state calculate the interest and bill you, or you file by paper or through software that supports the form.

If you cannot print, you can call the Comptroller at 1-800-638-2937, or 410-260-7980 from Central Maryland, to request a mailed copy. Order early, because mail delivery can take a week or more and the form is due with your return.

Step-by-Step: How to Fill Out Form 502UP Line by Line

Form 502UP has three blocks: the header, the underpayment computation (Lines 1–15), and the interest computation (Lines 16–18). Work top to bottom, and remember that Lines 11–15 use four columns, one per installment period. The four due dates are April 15, 2025, June 15, 2025, September 15, 2025, and January 15, 2026.

The Header: Name and Social Security Number

The top of the form asks for your first name, middle initial, last name, and Social Security number, plus the same for your spouse if you file jointly.

To answer it, print your name exactly as it appears on your Form 502 and your Social Security card, in CAPITAL letters, with the primary taxpayer listed first.

For example, DANIEL R PARK enters his name with SSN 214-55-0199, and his wife MAYA PARK follows on the spouse line.

A nuance comes up with name changes: if you married or divorced in 2025, use the name that matches your return for this year, not last year, so the form and return agree.

A common mistake is listing the spouse first on the 502UP but second on Form 502; the order must match, or the Comptroller may not link the form to the correct account, which delays processing.

A frequent misconception is that the header is just a formality. In truth, the state matches 502UP to your return by name and SSN, so a typo here can cause the whole form to be ignored and interest billed anyway.

Line 1: Total Maryland Income

Line 1 asks for your total Maryland income for 2025, the base figure everything else builds on.

Enter your Maryland adjusted gross income from Line 16 of Form 502 or Line 8 of Form 505NR; if you itemize, you may instead use taxable net income from Line 20 of Form 502 or Line 11 of Form 505NR.

For example, freelancer Carla Diaz pulls $96,400 from Line 16 of her Form 502 and writes it on Line 1.

A nuance: choosing the taxable-net-income option can slightly change your annualized percentages later, so pick one source and use it consistently across the form.

A common mistake is grabbing federal AGI instead of the Maryland figure, which inflates your income and overstates the required payment on Line 10.

A misconception is that Line 1 controls how much interest you owe. It does not directly; it mainly drives the annualized percentages in the second half of the form.

Lines 2 Through 4: Maryland Tax and Refundable Credits

These lines capture your 2025 tax and the refundable credits that reduce it. Line 2 is your Maryland and local tax, Line 3 is the refundable earned income credit, and Line 4 is other refundable income tax credits.

Enter Line 2 from Line 34 of Form 502 or Line 37 of Form 505, Line 3 from Line 44 of Form 502, and Line 4 from Line 45 of Form 502 or Line 48 of Form 505.

For example, Carla writes $6,180 on Line 2, leaves Line 3 blank because she gets no earned income credit, and writes $0 on Line 4.

A nuance: only refundable credits go here. Nonrefundable credits stay out, because they already reduced the Line 34 tax figure.

A common mistake is entering a nonrefundable credit on Line 4, which double-counts the benefit and understates the tax you needed to pay.

A misconception is that all credits lower your underpayment. Only refundable credits do on this form, so check each credit’s type before entering it.

Line 5: Tax on Tax Preference Items

Line 5 asks for the extra tax created by tax preference items, which apply to a small set of filers with items like certain depletion or interest.

To answer it, multiply the amount on Line 5 of Form 502TP by your highest state rate, then add Line 5 of Form 502TP times your local or special nonresident rate.

For example, most filers like Carla have none and simply enter $0.

A nuance: if you completed Form 502TP, you must finish it first, because Line 5 here pulls directly from that worksheet.

A common mistake is leaving Line 5 blank when you do have preference items, which understates the tax you owed and can trigger a later assessment.

A misconception is that everyone must compute this line. Most individual filers never touch Form 502TP and correctly enter zero.

Lines 6 Through 8: Building the 90% Safe Harbor

These lines turn your tax into the first safe harbor number. Line 6 adds Lines 3, 4, and 5; Line 7 subtracts Line 6 from Line 2; and Line 8 multiplies Line 7 by 90%.

Add the credits and preference tax on Line 6, subtract that total from your Line 2 tax to get Line 7, then multiply by .90 for Line 8.

For example, Carla’s Line 6 is $0, her Line 7 is $6,180, and her Line 8 is $5,562 (6,180 × 0.90).

A nuance: Line 8 represents the 90% of current-year tax safe harbor, one of the two ways to avoid interest entirely.

A common mistake is forgetting to subtract Line 6 before multiplying, which inflates Line 8 and makes your required payment look larger than it is.

A misconception is that 90% is a target you must hit at filing. It is the floor you needed to pay during the year through withholding and estimates.

Line 9: Prior-Year Tax and the 110% Safe Harbor

Line 9a asks for your 2024 tax, and Line 9b multiplies it by 110% to create the second safe harbor.

Enter on Line 9a your Line 34 of 2024 Form 502 (reduced by certain 502CR Part CC credits) or Line 37 of 2024 Form 505, then multiply by 1.10 for Line 9b.

For example, Carla’s 2024 tax was $5,000, so Line 9a is $5,000 and Line 9b is $5,500.

A nuance: if your 2024 return was amended or corrected, add the extra tax to Line 9a, because the safe harbor is based on your final 2024 liability.

A common mistake is pulling the wrong line from the 2024 return; using the refund or balance-due line instead of total tax overstates or understates the safe harbor and skews the entire form.

A misconception is that high earners can always use 110% of last year. Maryland uses 110% for everyone here, but the smaller of Line 8 or 9b still controls.

Line 10: Minimum Required Payment

Line 10 sets the minimum you needed to pay through withholding and estimates to avoid interest.

Enter the lesser of Line 8 or Line 9b; if you are a first-time Maryland filer with no 2024 return, enter Line 8.

For example, Carla compares Line 8 of $5,562 and Line 9b of $5,500, takes the smaller, and writes $5,500 on Line 10.

A nuance: first-time filers cannot use the prior-year safe harbor because there is no prior year, so they default to the 90% figure on Line 8.

A common mistake is taking the larger number, which overstates your required payment and creates a fake underpayment that costs you real interest.

A misconception is that Line 10 is what you owe now. It is the benchmark you should have already paid across the four quarters, not a payment due today.

Lines 11 Through 13: Spreading Income Across the Quarters

These lines split your income and required payment by installment period. Line 11 enters income per period, Line 12 turns it into a percentage of Line 1, and Line 13 multiplies Line 10 by that percentage.

If your income was even, enter one-fourth of Line 1 in column 1, one-half in column 2, three-fourths in column 3, and all of Line 1 in column 4; each column is cumulative. If income was uneven, enter actual income received through March 31, May 31, August 31, and December 31.

For example, with even income Carla puts $24,100, $48,200, $72,300, and $96,400 on Line 11, giving 25%, 50%, 75%, and 100% on Line 12, and $1,375, $2,750, $4,125, and $5,500 on Line 13.

A nuance: the annualized method on Line 11 is the escape hatch for someone whose income landed mostly late in the year, because it lowers the required payment for early quarters.

A common mistake is treating each column as standalone instead of cumulative, which scrambles every later calculation.

A misconception is that everyone benefits from the actual-dates method. It only helps if your income was lumpy; if it was steady, the even split is simpler and identical.

Line 14: Payments and Withholding Per Period

Line 14 asks how much you actually paid by each due date through estimates and withholding.

Enter the cumulative sum of estimated payments and Maryland tax withheld from the start of the year to each due date, including nonresident tax paid for you by a pass-through entity.

For example, if Carla had $1,000 withheld each quarter, her Line 14 reads $1,000, $2,000, $3,000, and $4,000.

A nuance: withholding is treated as paid evenly across the year even if it was lumpy, which often helps W-2 earners with side income.

A common mistake is trying to use a later overpayment to fix an earlier shortfall; Maryland does not let a big Q4 payment cure a Q1 underpayment.

A misconception is that estimated payments only count in the quarter you paid them. They count cumulatively, so a March payment helps every later column too.

Line 15: Underpayment Per Period

Line 15 is the heart of the form: it shows how short you were each quarter.

Subtract Line 14 from Line 13 in each column; if the result is less than zero, enter zero.

For example, in column 1 Carla’s Line 13 is $1,375 and Line 14 is $1,000, so Line 15 is $375; by column 4 her shortfall has grown to $1,500.

A nuance: a zero in a column means that quarter is fine, but a later column can still show an underpayment as the required amount climbs.

A common mistake is entering a negative number instead of zero, which wrongly reduces interest in other columns.

A misconception is that one paid-up quarter clears the year. Each quarter stands alone, so you can owe interest on Q1 even after catching up in Q4.

Lines 16 Through 18: Computing the Interest

The final block converts each quarter’s underpayment into dollars of interest. Line 16 holds the interest factors (0.0192, 0.0289, 0.0381, 0.0266), Line 17 multiplies each Line 15 underpayment by its factor, and Line 18 adds them up.

Multiply each column’s Line 15 by the matching Line 16 factor, write the result on Line 17, then total all four on Line 18 and carry it to Line 51 of Form 502 or Line 54 of Form 505.

For example, Carla’s column-1 underpayment of $375 times 0.0192 is about $7.20, and after all four quarters her Line 18 total is roughly $92.

A nuance: if a late payment landed between two due dates, you adjust the factor using the annual rate (11.4825% for the first three periods, 10.8133% for the fourth), counting any partial month as a full month.

A common mistake is using the prior year’s factors from an old form; the 2025 factors changed midyear, so an outdated PDF gives the wrong interest.

A misconception is that Line 18 is optional. If you owe it, it becomes part of your total payment with the return, and skipping it leaves a balance the state will bill.

Three Filled-Out Examples Using Real Scenarios

The scenarios below show how three common filers move through Form 502UP from header to Line 18. Each one faces a different reason for underpaying.

Scenario 1 — Carla Diaz, self-employed freelancer who underpaid all year

Form Section	What Carla Enters
Header	CARLA DIAZ, SSN 301-22-7788, single
Line 1 (Total Maryland income)	$96,400
Line 2 (2025 tax)	$6,180
Line 8 (90% safe harbor)	$5,562
Line 9b (110% of 2024 tax)	$5,500
Line 10 (minimum required)	$5,500
Line 13 (required per period)	$1,375 / $2,750 / $4,125 / $5,500
Line 14 (paid per period)	$1,000 / $2,000 / $3,000 / $4,000
Line 18 (total interest)	about $92

Scenario 2 — Walter Reed, retiree with a large one-time IRA withdrawal

Form Section	What Walter Enters
Header	WALTER J REED, SSN 188-40-2231, married filing jointly
Line 1 (Total Maryland income)	$120,000
Line 2 (2025 tax)	$8,400
Line 8 (90% safe harbor)	$7,560
Line 9b (110% of 2024 tax)	$4,950
Line 10 (minimum required)	$4,950
Line 14 (withholding per period)	$900 / $1,800 / $2,700 / $3,600
Line 15 (underpayment per period)	$337 / $675 / $1,012 / $1,350
Line 18 (total interest)	about $108

Scenario 3 — Priya Shah, investor with a big Q4 capital gain using annualization

Form Section	What Priya Enters
Header	PRIYA SHAH, SSN 422-19-6610, single
Line 1 (Total Maryland income)	$210,000
Line 10 (minimum required)	$13,800
Line 11 (annualized income)	$15,000 / $30,000 / $60,000 / $210,000
Line 12 (percent per period)	7% / 14% / 29% / 100%
Line 13 (required per period)	$966 / $1,932 / $4,002 / $13,800
Line 14 (paid per period)	$1,000 / $2,000 / $4,500 / $11,000
Line 18 (total interest, code 301)	about $310

Priya’s late capital gain means her early quarters show little required payment, so the annualized method on Lines 11–15 protects her from interest on income she had not yet earned. Because her uneven income reduced the interest, she enters code 301 on her Form 502 and attaches the 502UP.

How to File the Completed Form 502UP

Form 502UP is never filed alone; you attach it to your main return and submit them together. The instructions on the 2025 form state plainly to attach this form to Form 502, 505, or 515. Below are the channels available.

By mail. Attach 502UP behind your completed Form 502 and mail to the address printed in the Form 502 instructions for a balance-due return, generally the Comptroller of Maryland in Annapolis. There is no separate fee for the form; you simply include your interest from Line 18 in your total payment. Pay by check or money order payable to Comptroller of Maryland with your SSN and “2025 Form 502” on the memo line, and keep a copy plus your certified-mail receipt as proof of filing.

Through tax software. Programs like TurboTax, FreeTaxUSA, and TaxSlayer generate 502UP and e-file it with your return. The fee is the software’s price, payment is by card, processing runs a few weeks, and your proof is the electronic acceptance confirmation. Review the four annualized columns by hand, because some programs handle them poorly.

With a tax professional. A CPA or enrolled agent completes and e-files the form as part of your return. Fees vary by preparer, and your proof of filing is the signed Form 8879-equivalent authorization and the acceptance record they provide.

Through Maryland iFile. You cannot complete 502UP in iFile for 2025. If you file there and owe more than $500, let the state compute the interest and send a bill, or switch to paper or software to claim the uneven-income method yourself.

What Happens After You File

Once your return and 502UP are processed, the Comptroller verifies your Line 18 interest against its own records. If your numbers match and you included the interest in your payment, the matter closes with no further notice, which is the outcome you want.

If you chose to let the state figure the interest and did not file 502UP, Maryland calculates the amount and mails you an assessment notice. This notice shows the interest due and a due date, and the interest keeps growing at the monthly rate until you pay, so respond fast.

If you claimed the uneven-income method with code 301, or the farmer/fisherman or other-state exceptions with codes 300 or 302, the Comptroller reviews the attached form to confirm the reduced or zero interest. Keep your month-by-month income records, because the state can ask you to support the annualized columns.

A real-world example: Marcus Lee let the state calculate his interest, ignored the first notice, and watched a $140 charge grow as monthly interest compounded before he finally paid. Acting on the first notice would have saved him money.

Mistakes to Avoid When Filling Out the Form

• Using an outdated form. Old interest factors produce the wrong Line 18, so you under- or overpay and may get a corrected bill.
• Filing when you qualify for the $500 exception. If your tax after withholding is $500 or less, filing is unnecessary and can confuse processing.
• Pulling federal AGI for Line 1. Federal income overstates the Maryland base and inflates your required payment.
• Taking the larger of Line 8 and Line 9b on Line 10. This creates a false underpayment and real interest you did not owe.
• Entering the wrong 2024 tax on Line 9a. A bad prior-year number breaks the 110% safe harbor and skews the whole form.
• Treating columns as standalone instead of cumulative. Non-cumulative entries on Lines 11 and 14 scramble every later calculation.
• Using a Q4 overpayment to cover a Q1 shortfall. Maryland forbids this, so the early underpayment still earns interest.
• Entering negative numbers on Line 15. Negatives wrongly reduce interest; the floor is zero.
• Forgetting to attach the form to Form 502. A detached 502UP may be ignored, and the state bills you anyway.
• Skipping the code number for uneven income. Without code 301, the Comptroller may not honor your annualized reduction.
• Omitting nonresident tax paid by a pass-through entity on Line 14. Leaving it out overstates your underpayment.
• Listing the spouse in a different order than on Form 502. A mismatch can detach the form from your account.

Do’s and Don’ts

Do:

• Do confirm the revision stamp reads 09/25 so your interest factors are current.
• Do finish your Form 502 first, because nearly every 502UP line pulls from it.
• Do use the annualized method if your income was lumpy, since it can erase interest.
• Do enter the correct code number (300, 301, or 302) when claiming an exception.
• Do keep proof of every estimated payment, since Line 14 depends on exact dates and amounts.
• Do pay even a little early, because interest accrues by the month.

Don’t:

• Don’t file at all if you clearly meet the $500 or safe harbor exception.
• Don’t guess your 2024 tax on Line 9a; a wrong figure costs real money.
• Don’t mix income sources between AGI and taxable net income on Line 1.
• Don’t ignore a state assessment notice, because interest keeps compounding.
• Don’t assume software got the columns right; review Lines 11–15 by hand.
• Don’t forget to carry Line 18 to Line 51 of Form 502 or Line 54 of Form 505.

Pros and Cons of Filing on Your Own vs. With Help

Deciding whether to complete Form 502UP yourself or let a pro handle it depends on how uneven your income was and how comfortable you are with the four-column math.

Pros of filing on your own:

• You save preparer fees, since the form is short once your return is done.
• You control the annualized method and can fine-tune the columns to lower interest.
• You learn your safe harbor numbers, which helps you plan next year’s estimates.
• You avoid the state’s default calculation, which never uses the uneven-income break.
• You keep your records organized, making future filings faster.

Cons of filing on your own:

• The four cumulative columns confuse many filers, leading to errors.
• A wrong prior-year figure quietly inflates your interest.
• Software may mishandle annualization, so you must double-check.
• You bear the risk if the Comptroller questions your code-301 reduction.
• It takes time to gather payment dates and 2024 figures.

Pros of using a professional: a CPA catches the cumulative-column traps, applies the right safe harbor, and signs off on the annualized reduction, which lowers your audit risk. Cons: you pay a fee, you still must hand over accurate records, and a rushed preparer can use the state’s default method that ignores your uneven income.

FAQs

Do I have to file Form 502UP if I owe less than $500 after withholding?

No. If your tax liability after subtracting Maryland withholding is $500 or less, no interest is due and you should not file the form at all.

Do I write my income from Form 502 Line 16 on Line 1?

Yes. Enter Maryland adjusted gross income from Line 16 of Form 502 or Line 8 of Form 505NR; itemizers may instead use taxable net income.

Do I use the larger of Line 8 or Line 9b on Line 10?

No. Line 10 takes the lesser of the two; using the larger creates a false underpayment and real interest you do not owe.

Do I enter my 2024 tax or my 2024 refund on Line 9a?

No. Enter your 2024 tax from Line 34 of the 2024 Form 502 or Line 37 of Form 505, not your refund or balance due.

Do the columns on Lines 11 and 14 carry over from one to the next?

Yes. Each successive column is cumulative and includes all prior columns, so a March payment also counts in later quarters.

Do I file 502UP if my income arrived unevenly during the year?

Yes. File it and use the annualized method on Lines 11–15, then enter code 301 on Form 502 to claim the reduced interest.

Do I have to figure the interest myself?

No. You may complete your return as usual, skip Form 502UP, and let the Comptroller calculate the interest and send you a bill.

Do first-time Maryland filers use the 110% safe harbor?

No. With no prior-year return, first-time filers cannot use Line 9b and must enter the Line 8 amount on Line 10.

Do estimated payments and withholding both count on Line 14?

Yes. Add estimated payments and Maryland tax withheld together, including nonresident tax paid by a pass-through entity on your behalf.

Do I attach Form 502UP to my return or mail it separately?

Yes, attach it. The form must be filed with Form 502, 505, or 515; a detached 502UP can be ignored.

Do I owe interest if 90% of my income is taxed by another state?

No. If at least 90% of your taxable income is taxable elsewhere and the underpayment is only county tax, no interest is due; use code 302.

Do farmers and fishermen fill out the form the same way?

No. They complete Lines 1–10, carry Line 10 to column 4 of Line 13, fill only column 4, and may use code 300.

Do I carry the Line 18 total to my main return?

Yes. Place the Line 18 interest in the box on Line 51 of Form 502 or Line 54 of Form 505 and include it in your payment.

Do tax preference items affect Line 5 for most filers?

No. Most individuals have no Form 502TP items and correctly enter zero on Line 5.