How to Fill Out North Carolina Industrial Commission Form 21 + FAQs

North Carolina Industrial Commission Form 21 is the Agreement for Compensation for Disability, the written deal that an injured worker, the employer, and the insurance carrier sign to lock in the weekly check amount, the start date, and the type of disability benefits owed under a workers’ comp claim. It is filed with the North Carolina Industrial Commission under the authority of G.S. § 97-82, and once a claims examiner approves it, the agreement becomes a binding award that carries the same legal weight as a court order.

This form matters because the numbers written on it follow you for years. A wrong average weekly wage, a missed start date, or a misread “type of disability” box can shrink your checks, end them early, or cost you the right to future medical care. About 30,000 to 40,000 new injury claims are reported to the Commission each year, and a large share of the accepted ones are resolved through agreement forms like the Form 21, so getting it right is not a rare event — it is the normal path most accepted claims travel.

Here is what you will learn in this guide:

• 📋 What every box on Form 21 means and exactly what to write in it
• 💵 How the average weekly wage and compensation rate are figured and why they control your check
• 🧑‍⚖️ Who signs, who approves, and the 20-day filing rule that keeps your claim moving
• 🗂️ How to file through the Electronic Document Filing Portal step by step
• ⚠️ The field-level mistakes that delay checks or kill future benefits — and how to dodge them

What the Form Is and Who Must File It

Form 21 is the official agreement that says the employer and the insurance carrier accept your claim and agree to pay you disability benefits at a set weekly rate. The full title printed at the top is Agreement for Compensation for Disability, and the revision date in the bottom corner reads 3/2021, so check that date to be sure you have the current version. The form is authorized by G.S. § 97-82, and its exact wording is set by rule in 11 NCAC 23L .0101.

The agency that receives and approves the form is the North Carolina Industrial Commission, the state body that runs the workers’ comp system. A claims examiner reviews the agreement, and only after that examiner signs the “The Foregoing Agreement Is Hereby Approved” block does the deal become an enforceable award.

In practice, the employer or the insurance carrier prepares Form 21, not the injured worker. The carrier fills in the wage math and the benefit terms, then sends it to the worker to sign. The worker’s job is to read every line, make sure the numbers are right, and sign only when the terms match reality. The employer and carrier sign too, which is why the rule names them the parties responsible for submitting the executed form to the Commission.

You will run into Form 21 when your claim is accepted and you are out of work, or when you have a permanent rating to a body part. It is not used to deny a claim and it is not used for a full and final settlement of everything. It is the “we agree you are owed ongoing or scheduled benefits” document, which keeps your claim open rather than closing it for good.

Before You Start: Documents and Information You Need

Gather everything before you open the form, because a single missing number can stall approval or lock in a wrong figure. The carrier prepares the form, but you should hold the same records so you can check their math line by line. Here is the pre-filing checklist:

• Your Form 18. This is your Notice of Accident that started the claim; it holds the names, dates, and wage figures the Form 21 must match, and a mismatch invites delay.
• Your wage records for the 52 weeks before the injury. These pay stubs prove your average weekly wage; without them you cannot tell if the carrier’s rate is too low.
• The exact date of injury. This anchors which wage period and which law version apply, and a wrong date can shift your whole rate.
• The date you first lost time from work. This sets when checks start and whether the 7-day waiting period applies; missing it can cost you a week of pay.
• Your Social Security number. Only the last four digits go on the form, but the Commission uses them to match your file, so an error misroutes your case.
• Your current mailing address. Your checks and notices go here; an old address means lost checks and missed deadlines.
• The insurance carrier and adjuster details. The carrier name, address, and file number tie the form to the right policy, and a blank here slows routing.
• Any permanent impairment rating report. If you have a doctor’s rating, you need the percentage and the body part to fill the disability section, and a guess here can underpay you.
• Your employer’s legal name and code number. The Commission tracks employers by code; the wrong name can attach your benefits to the wrong company.
• Attorney contact information, if you have one. The form has an attorney signature line and an attorney fee box, and leaving it blank when you are represented can muddle the fee approval.

If any item is missing, do not guess. A blank or estimated figure can become a binding number once the examiner approves the form, and undoing it later means filing more paperwork and waiting weeks.

Where to Get the Form and How to Access It

The official Form 21 lives on the Commission’s website. You can download it from the N.C. Industrial Commission forms page, where every current form is posted in a fillable PDF format that the Commission updated for electronic filing. Always pull the form from this page rather than a third-party site, because older copies may carry a stale revision date and the Commission can reject a form that is not the current 3/2021 version.

Because the employer or carrier usually drafts Form 21, an injured worker often first sees it as a PDF emailed by the adjuster or handed over by the employer. That is normal. You still have the right to download a blank copy yourself and compare it field by field against what the carrier sent, which is the best way to catch a wrong wage or a missing date before you sign.

If you cannot access the website or need a copy mailed to you, call the Commission’s helpline at (800) 688-8349 and ask Claims Administration to send the current form. The same number is printed on the form itself under the “Need Assistance?” notice for filers who do not have an attorney.

The form is two pages. Page 1 holds the parties’ information, the agreement terms, and the signature and approval blocks. Page 2 holds the “Important Notices to Employee” that explain your deadlines for future checks and future medical care. Read page 2 closely, because you certify in writing that you read it when you sign.

Step-by-Step: How to Fill Out Form 21 Line by Line

Work through the form in the order the fields appear. The carrier completes most boxes, but you should verify each one. Below, every field gets its own walkthrough so you know what it asks, how to answer, what a correct entry looks like, the edge cases, the common mistake, and the myth to drop.

IC File # and the Code Number Boxes

The top of the form has four boxes: IC File #, Emp. Code #, Carrier Code #, and Carrier File #. In plain English, these are the tracking numbers the Commission and the insurance company use to find your case fast.

To answer, copy the IC File number from any prior Commission notice or from your Form 18 acknowledgment; the carrier fills the three code and file numbers from its own records. Use the exact digits with no extra spaces. For example, Maria Lopez writes IC File # X1234567 in the top box, matching the number on her claim notice.

A common edge case is a brand-new claim with no IC File number yet. If the Commission has not assigned one, leave the IC File # blank and let the examiner add it; do not invent a number. The most common mistake is transposing two digits in the file number, and the direct consequence is that the form lands in the wrong file or sits unmatched while your checks wait. A myth worth dropping is that these boxes are optional clutter — they are the routing labels, and a wrong code can attach your benefits to another worker’s claim.

Employee’s Name, Address, City, State, Zip

This block asks for the injured worker’s full legal name and current mailing address. Plain and simple, it tells the Commission who is owed money and where to send the checks and notices.

Write your full legal name as it appears on your Social Security card, then your street address, city, state, and ZIP on the lines provided. Use your real mailing address, not a job site. For example, Maria Lopez writes her name and 418 Oak Street, Durham, NC 27701 below it.

If you have a P.O. Box, use it on the address line so mail reaches you, even if your home is a separate street address. The common mistake here is listing an old address after a move, and the consequence is that your checks and your deadline notices go to the wrong place, which can cost you money and rights. A frequent misconception is that a nickname or shortened name is fine; the Commission cross-checks names, so use your legal name to avoid a matching hold.

Home Telephone and Work Telephone

This field asks for the phone numbers where the Commission or carrier can reach you. It exists so the parties can clear up questions without delaying the claim.

Enter your home or cell number and your work number using the area code, like (919) 555-0142. If you no longer work for the employer, you can leave the work number blank or write N/A. For example, Maria lists her cell as her home number because she has no landline.

The edge case is a worker who has been let go after the injury; a missing work number is fine, so do not feel forced to fill it. The common mistake is giving a disconnected number, and the consequence is that the adjuster cannot reach you to resolve a wage question, which stalls the form. The myth is that the phone line does not matter once the form is signed — it does, because post-approval questions about checks often start with a phone call.

Last 4 Digits of Social Security Number, Sex, Date of Birth

This line asks for the last four digits of your Social Security number, your sex (a box for M or F), and your date of birth. These details let the Commission match the form to the right person in its system.

Write only the last four digits of your SSN, check the correct sex box, and enter your date of birth as MM/DD/YYYY. For example, Maria writes 0142, checks F, and writes 03/14/1985. Never write your full nine-digit SSN, because the form asks for only the last four.

A common edge case is a worker whose legal documents show a different birth date than memory; always use the date on your official ID. The mistake filers make is writing the full Social Security number, which is a privacy risk and not what the box asks. The misconception is that the date of birth is filler — it is a key matching field, and a wrong year can pull up the wrong file.

Employer’s Name and Telephone Number

This block asks for the legal name of your employer and the employer’s phone number. It identifies the business on the hook for your benefits through its insurance.

Enter the employer’s exact legal name, not a brand or store nickname, and add the main phone number. For example, Piedmont Logistics LLC, (336) 555-0190 goes on the line. Match the name to what is on your pay stub or your Form 18.

The edge case is a staffing agency or a parent company; if a temp agency employed you, list the agency as the employer unless your claim says otherwise. The common mistake is writing the trade name instead of the legal entity, and the consequence is that the Commission may attach your claim to the wrong company or none at all. The myth is that any version of the company name works — it does not, because benefits track the legal employer of record.

Employer’s Address, City, State, Zip

This field asks for the employer’s mailing address. It tells the Commission where to send employer notices about the agreement.

Enter the employer’s street address, city, state, and ZIP. For example, 2200 Industrial Drive, Greensboro, NC 27406. Use the address for the location that employs you if the company has several.

The edge case is a multi-site employer; use the address of the office that handles human resources or payroll so notices reach the right desk. The common mistake is using the job-site address when payroll sits elsewhere, and the consequence is that employer notices get lost. The misconception is that the carrier handles all mail so the employer address is unimportant — both parties get notices, and a wrong employer address can delay an employer response.

Insurance Carrier, Carrier’s Address, Telephone, and Fax

This block asks for the workers’ comp insurance carrier’s name, address, phone, and fax. It links the agreement to the insurance policy that actually pays your checks.

The carrier fills these in from its own records. Confirm the carrier name matches the company sending your checks. For example, Granite State Insurance Co., 1500 Carrier Way, Charlotte, NC 28202, (704) 555-0177. If a third-party administrator handles the claim, its name may appear here too.

The edge case is a self-insured employer with no outside carrier; in that case the employer’s claims unit or its administrator fills this block. The common mistake is an outdated carrier name after the employer switched insurers, and the consequence is that payment routing breaks and checks stall. The myth is that the carrier block is just for the insurance company’s benefit — it protects you, because a correct carrier is who you chase if a check is late.

The Stipulation Section — “We, The Undersigned, Do Hereby Agree And Stipulate As Follows”

This is the heart of the form. The blank lines under “We, The Undersigned, Do Hereby Agree And Stipulate As Follows” hold the actual terms: the date of injury, the body part hurt, the average weekly wage, the compensation rate, the type of disability, the date disability began, and the number of weeks of payment. In plain English, this is where the deal is spelled out in dollars and dates.

To answer, the carrier states the facts in order: the date of accident, a short description of the injury, the average weekly wage, the resulting compensation rate, the kind of disability (temporary total, temporary partial, or permanent partial), the date benefits start, and how long they run. For example, the section may read that Maria Lopez suffered a back injury on 02/10/2026, had an average weekly wage of $720.00, yielding a compensation rate of $480.06 per week for temporary total disability beginning 02/18/2026. Each figure must trace back to your wage records and medical notes.

The average weekly wage drives everything, and G.S. § 97-2(5) sets five methods to figure it; the usual one divides your total earnings in the 52 weeks before injury by 52, and it must include overtime, bonuses, and allowances. The compensation rate for total disability is two-thirds of that average weekly wage, capped at the state maximum for the year of injury. A common edge case is a worker employed under a year, where the carrier divides total wages by the weeks actually worked instead of 52.

The most common and most damaging mistake in this section is an understated average weekly wage, often because the carrier left out overtime or bonuses, and the consequence is that every check for the life of the claim is too small. The misconception many workers hold is that the rate equals their old paycheck — it does not, because the rate is roughly two-thirds of the average weekly wage and is capped, so it is normal for it to be lower than full pay, but it should never be lower than the correct two-thirds figure.

Employer and Carrier Signature Blocks

After the terms, the form has signature lines reading Name Of Employer / Signature / Title and Name Of Carrier / Administrator / Signature / Title. This is where the paying parties commit to the deal.

The employer’s representative and the carrier or administrator each print a name, sign, and add a title such as Adjuster or HR Manager. For example, James Reed, Adjuster, signs for Granite State Insurance. These signatures show the employer and insurer accept the terms before the worker signs.

The edge case is a self-insured employer, where one administrator may sign both as employer and carrier. The common mistake is an unsigned carrier line, and the consequence is that the Commission cannot approve an incomplete agreement, so it bounces back. The misconception is that the worker signs first — usually the paying parties execute the terms, then the worker reviews and signs, which protects the worker from agreeing to blank terms.

Employee Signature and the Page 2 Certification

This line reads Signature of Employee / Address and includes a certification that says, “By signing I enter into this agreement and certify that I have read the ‘Important Notices to Employee’ printed on Page 2 of this form.” In plain English, your signature makes the deal binding and confirms you read your rights notice.

Sign your name and write your address on the line. Do this only after you have read page 2 and confirmed every number on page 1 is right. For example, Maria Lopez signs and writes her Durham address after checking that her wage and rate are correct.

The edge case is a worker who disagrees with a figure; do not sign — raise the issue with the adjuster or the Commission first, because your signature locks in the terms. The common mistake is signing before reading page 2, and the consequence is that you may miss the two-year deadlines for future checks and future medical care described there. The misconception is that signing is just a formality — it is the act that turns the form into a binding award, so treat it with care.

Signature of Employee’s Attorney

This line asks for your attorney’s signature and address, if you have one. It confirms a lawyer reviewed the deal on your behalf.

If you are represented, your attorney signs and lists the firm address. For example, Attorney Dana Whitfield, 100 Fayetteville St., Raleigh, NC 27601. If you have no attorney, leave this line blank.

The edge case is a worker who hires counsel midway; the attorney who is active at signing should sign. The common mistake is a represented worker signing without the attorney’s review, and the consequence is that you may accept a low wage figure your lawyer would have challenged. The misconception is that signing this line waives anything — it does not, it simply records that counsel was involved.

North Carolina Industrial Commission Approval Block

At the bottom sits the Commission’s section: “The Foregoing Agreement Is Hereby Approved,” with a Claims Examiner signature and Date line, an Attorney’s Fee Approved line, a “Check Box If No Attorney Retained” box, and a “Check Box If Employee Is In Managed Care” box. This is the official stamp that turns the agreement into an award.

You do not fill this part — a claims examiner does. The examiner signs, dates, approves any attorney fee, and checks the boxes for no attorney or managed care as they apply. For example, the examiner checks “No Attorney Retained” for a pro se worker like Maria.

The edge case is an attorney fee that needs separate approval; the examiner reviews and approves the fee on this line so it is paid out of, not on top of, your benefits. The common mistake parties make is submitting the form before both the worker and carrier have signed, and the consequence is that the examiner returns it unapproved. The misconception is that a signed agreement is binding the moment the parties sign — it is not fully enforceable until the examiner approves it here.

Three Filled-Out Examples Using Real Scenarios

These walkthroughs follow three workers through the most common Form 21 situations. Each table shows the key entries for that worker’s agreement.

Scenario 1: Maria Lopez, temporary total disability after a back injury. Maria is out of work entirely while she heals, so her agreement sets ongoing weekly checks.

Form Section	What Maria Enters or Confirms
Employee’s Name	Maria Lopez
Address	418 Oak Street, Durham, NC 27701
Last 4 of SSN / Sex / DOB	0142 / F / 03/14/1985
Employer’s Name	Piedmont Logistics LLC
Insurance Carrier	Granite State Insurance Co.
Date of Injury (stipulation)	02/10/2026
Average Weekly Wage	$720.00
Compensation Rate	$480.06 per week
Type of Disability	Temporary total disability
Date Disability Began	02/18/2026
Employee Signature	Maria Lopez, signed after reading page 2

Scenario 2: Carlos Mendez, permanent partial disability for a rated hand. Carlos returned to work but a doctor gave his hand a permanent rating, so his agreement pays a set number of weeks for that body part.

Form Section	What Carlos Enters or Confirms
Employee’s Name	Carlos Mendez
Address	77 Pine Ridge Rd., Asheville, NC 28801
Last 4 of SSN / Sex / DOB	3318 / M / 06/22/1979
Employer’s Name	Blue Ridge Manufacturing Inc.
Insurance Carrier	Carolina Mutual Comp
Date of Injury (stipulation)	09/05/2025
Average Weekly Wage	$960.00
Compensation Rate	$640.08 per week
Type of Disability	Permanent partial — 15% rating to the right hand
Number of Weeks	30 weeks (15% of 200 weeks for a hand)
Employee Signature	Carlos Mendez, signed after attorney review

Scenario 3: Aisha Bell, temporary partial disability on lighter, lower-paying work. Aisha went back to a light-duty job that pays less than her old role, so her agreement pays a partial benefit to bridge the wage gap.

Form Section	What Aisha Enters or Confirms
Employee’s Name	Aisha Bell
Address	905 Maple Ave., Wilmington, NC 28401
Last 4 of SSN / Sex / DOB	5520 / F / 11/30/1990
Employer’s Name	Coastal Retail Group LLC
Insurance Carrier	Atlantic Indemnity Co.
Date of Injury (stipulation)	01/12/2026
Average Weekly Wage	$600.00
Reduced Weekly Earnings	$360.00 on light duty
Type of Disability	Temporary partial disability
Compensation Rate	$160.00 per week (two-thirds of the $240 wage loss)
Date Disability Began	01/20/2026
Employee Signature	Aisha Bell, signed after confirming wage figures

How to File the Completed Form

Filing is now electronic, and the Electronic Document Filing Portal, called the EDFP, is the required channel for self-insured employers and carriers. The party that prepares the form — the employer or carrier — submits it, not the injured worker. The rule in 11 NCAC 23A .0501 gives the employer or carrier 20 days after receiving the form signed by the employee to submit it to the Commission.

Here is how each channel works:

• Electronic Document Filing Portal (EDFP). This is the main and required route. The carrier registers an account on the NCIC Online Services Center, uploads the signed PDF, and submits it. There is no filing fee for a Form 21 agreement. Processing time runs from a few days to a few weeks depending on the examiner’s queue, and the portal gives a confirmation receipt the filer should save as proof of filing.
• Email backup. If the portal is down, the Commission accepts forms by email to edfp@ic.nc.gov. Keep the sent email and any auto-reply as your proof of filing. There is no fee.
• By mail. Paper filing is largely phased out for these agreements, but if mail is used, send it to the N.C. Industrial Commission at the Mail Service Center in Raleigh, NC 27699 and keep a certified-mail receipt as proof. No fee applies.
• By phone for help. You cannot file by phone, but you can call (919) 807-2502 for Claims Administration or the (800) 688-8349 helpline for guidance, and (919) 807-2695 for portal support.

As the injured worker, your role at filing is to confirm the carrier actually submitted the form and to ask for a copy of the filed version. Keep your signed copy, because the rule requires the employer to give you a copy when you sign.

What Happens After You File

Once the Form 21 reaches the Commission, a claims examiner reviews it for completeness and fairness. The examiner checks that the average weekly wage and compensation rate are correct and that both parties signed, then signs the approval block at the bottom. Approval is what turns the agreement into a binding award with the force of a Commission order.

After approval, your checks should arrive on the schedule the agreement sets, usually weekly, though the Commission can allow monthly payments in some cases. If the carrier already started payments, approval confirms they continue at the agreed rate. Keep every check stub, because those records prove what you were paid and when.

When payments stop, the carrier must file a Form 28B, Report of Compensation Paid, within 16 days of the last payment or face a penalty. That form tells the Commission the total paid and is your record of what the claim has covered so far. Watch for it, because it also starts the clock on your future-benefit deadlines.

The page 2 notices warn that if you later want more checks, you must notify the Commission in writing within two years of your last compensation check, and your right to future medical care ends two years after the last medical or other compensation payment. To protect future medical care, you can file a Form 18M for additional medical compensation or a Form 33 to request a hearing under G.S. § 97-25.1.

Mistakes to Avoid When Filling Out the Form

Each error below has cost real workers money or rights, so check the form against this list before anyone signes.

• Understating the average weekly wage by leaving out overtime or bonuses lowers every check for the life of the claim.
• Using the wrong date of injury can shift your wage period and apply the wrong year’s benefit cap.
• Listing an old mailing address sends your checks and deadline notices to the wrong place.
• Writing your full Social Security number instead of only the last four creates a privacy risk and ignores the box’s instruction.
• Naming the employer’s trade name instead of its legal entity can attach your claim to the wrong company.
• Leaving the carrier block outdated after an insurer change breaks payment routing and delays checks.
• Misstating the type of disability — total versus partial — changes how your rate and weeks are figured and can underpay you.
• Skipping the date disability began can cost you a week of pay tied to the 7-day waiting period.
• Signing before reading page 2 means you may miss the two-year deadlines for future checks and medical care.
• Submitting the form before both the worker and carrier sign forces the examiner to return it unapproved.
• A represented worker signing without attorney review can lock in a low figure a lawyer would have challenged.
• Treating the agreement as a full and final settlement is wrong, because Form 21 keeps the claim open and does not close future rights.

Do’s and Don’ts

Follow these habits to keep your agreement clean and your benefits protected.

Do:

• Do compare the carrier’s wage figure against your own 52 weeks of pay stubs, because the rate flows from it.
• Do read page 2 in full before signing, because you certify that you read it.
• Do confirm the type of disability matches your work status, since it controls your rate and weeks.
• Do keep a signed copy of the form, because the rule entitles you to one.
• Do verify the carrier filed the form within 20 days, since that keeps your claim moving.
• Do call the helpline at (800) 688-8349 if a number looks wrong and you have no attorney.

Don’t:

• Don’t sign while any figure is blank or unclear, because your signature makes it binding.
• Don’t accept an average weekly wage that ignores overtime, since it shrinks every check.
• Don’t use a job-site address when payroll and notices go elsewhere, or mail will be lost.
• Don’t assume Form 21 settles your claim for good, because it keeps the claim open.
• Don’t ignore the two-year deadlines on page 2, or you may lose future benefits.
• Don’t let the carrier rush your signature, since you have the right to review first.

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

Form 21 is prepared by the carrier, but whether you review and sign it alone or with an attorney changes your odds of catching errors. Weigh these points.

Pros of handling it on your own:

• You avoid attorney fees, which are taken out of your benefits when approved.
• You control the timing and can sign as soon as the numbers check out.
• For simple claims with clear wages, the math is easy to verify yourself.
• You deal directly with the adjuster, which can speed small fixes.
• You keep the full benefit amount with no fee deduction.

Cons of handling it on your own:

• You may miss an understated average weekly wage that a lawyer would catch.
• You might not know the correct number of weeks for a body-part rating.
• You could overlook the page 2 deadlines that protect future benefits.
• You have less leverage to push back on a low rate.
• A binding award is hard to undo once the examiner approves it.

FAQs

Is Form 21 the same as a final settlement of my claim?

No. Form 21 is an agreement for ongoing or scheduled disability benefits that keeps your claim open. A full and final settlement uses a separate clincher agreement, not the Form 21.

Is the employer or carrier responsible for filing Form 21?

Yes. The employer or carrier prepares and submits the form, and the rule gives them 20 days after you sign it to file it with the Commission.

Is the compensation rate the same as my old paycheck?

No. For total disability the rate is about two-thirds of your average weekly wage, capped at the state maximum, so it is normally lower than your full pre-injury pay.

Do I write my full Social Security number on the form?

No. The form asks only for the last four digits of your Social Security number, so writing all nine is both a privacy risk and not what the box requests.

Is the average weekly wage supposed to include overtime and bonuses?

Yes. Under G.S. § 97-2(5), the average weekly wage includes overtime, bonuses, and allowances, so leaving them out lowers every check you receive.

Do I have to sign Form 21 if a figure looks wrong?

No. Do not sign while any number is wrong or blank. Raise the issue with the adjuster or the Commission first, because your signature locks in the terms.

Is the agreement binding the moment the parties sign it?

No. The agreement becomes an enforceable award only after a claims examiner signs the approval block at the bottom of the form.

Do I check the managed care box myself?

No. The claims examiner checks the “Employee Is In Managed Care” box and the “No Attorney Retained” box during the Commission’s approval review, not you.

Is there a filing fee for Form 21?

No. The Commission does not charge a fee to file a Form 21 agreement through the Electronic Document Filing Portal or by mail.

Do I write my work phone if I no longer have the job?

No. If you were let go after the injury, you can leave the work telephone line blank or write N/A; only a reachable number matters.

Is there a deadline to claim more checks after payments stop?

Yes. You must notify the Commission in writing within two years from the date you receive your last compensation check, or you may lose the right to those benefits.

Do I lose future medical care once my checks end?

Yes, eventually. Your right to future medical compensation ends two years after the last medical or other payment unless you file a Form 18M or a Form 33 to keep it open.

Is a P.O. Box acceptable in the address box?

Yes. You can list a P.O. Box on the address line so your checks and notices reach you, even if your home is at a separate street address.

Do I need an attorney to sign Form 21?

No. You can review and sign on your own, but a lawyer can catch a low wage figure or a wrong number of weeks, and the form has a line for an attorney signature if you have one.