How to Complete the New York C-4.3: MMI, SLU, and Filing

The New York C-4.3 form is the Doctor’s Report of MMI/Permanent Partial Impairment, filed by a treating physician or examining provider when an injured worker has reached maximum medical improvement and has a lasting impairment from a work-related injury. You complete three identification sections, answer the MMI question with a date, and fill in Attachment A for a schedule loss of use or Attachment B for a non-schedule injury (or both if separate injuries require it). The completed form is attached to an electronically filed CMS-1500 medical bill rather than sent to the Board on its own, and copies go to the carrier and the claimant’s representative.¹

When You File a C-4.3

You file the C-4.3 in one of two situations: when you form an independent opinion that your patient has reached MMI with a permanent partial impairment, or when the Workers’ Compensation Board directly asks you for that opinion. Both treating doctors and independent medical examiners use the same form.¹

A chiropractor, podiatrist, psychologist, nurse practitioner, or licensed clinical social worker may file if the injury falls within the scope of their license under New York’s Education Law. If it doesn’t, the provider must advise the injured worker to see a physician.¹

Sections A Through C: Identifiers That Must Match

Section A collects the patient’s full name, Social Security number, date of birth, address, and date of injury or illness, along with the WCB Case Number and Claim Administrator Claim Number at the top of the form and the date of examination. Every field must match what the Board already has on file. A transposed digit in the case number or a slight variation in the claimant’s name can route the report to the wrong file or trigger rejection.¹

Section B identifies you as the provider. Enter your name, WCB Authorization number, WCB Rating Code, Federal Tax ID, office address, phone number, and NPI number. The form must be signed by the attending doctor and carry the authorization certificate number and code letters. Without valid authorization credentials, the Board will not accept the report.

Section C captures the employer’s insurance carrier name and address, the Claim Administrator Claim Number if it differs from the one entered above, and the relevant diagnoses. Pull the carrier name and address from prior Board correspondence rather than from memory. If the carrier address is wrong, a required party never receives the report, and the case stalls.

The MMI Determination

The central question is whether the patient has reached maximum medical improvement. If yes, enter the specific date the claimant reached MMI. That date marks the legal shift from temporary disability to permanent impairment evaluation.¹

If the answer is no, explain why the patient has not reached MMI and describe the proposed treatment plan, attaching supporting documentation as needed. A “no” answer creates a record the Board uses to monitor treatment and schedule future review.

Attachment A: Schedule Loss of Use

Attachment A applies when the permanent impairment involves a body part covered by the schedule in Workers’ Compensation Law Section 15(3). Examine the injured extremity, measure range of motion, evaluate surgical outcomes, and assign a percentage of loss of use based on the Board’s Impairment Guidelines.² That percentage translates directly into weeks of compensation under the statutory schedule.

Maximum weeks for a total loss of the most common body parts:³

Arm: 312 weeks
Leg: 288 weeks
Hand: 244 weeks
Foot: 205 weeks
Eye: 160 weeks
Hearing, both ears: 150 weeks
Thumb: 75 weeks
First finger: 46 weeks
Great toe: 38 weeks

A partial loss gets a proportional share. Fifty percent loss of use of an arm produces a 156-week award. The weekly rate is two-thirds of the claimant’s average weekly wages, subject to the statutory maximum.³

Document the clinical findings and measurements that support the percentage you assigned. Vague conclusions without objective exam data will not survive a challenge from the carrier. The Impairment Guidelines organize evaluations by body region, with chapters on upper extremities (thumb and fingers, hand and wrist, elbow, shoulder), lower extremities, and other scheduled body parts, and each chapter provides range-of-motion measurement protocols and calculation methods specific to that body part.² Departing from those protocols gives the carrier grounds to dispute the rating.

Attachment B: Non-Schedule Injuries

Attachment B covers injuries outside the schedule: primarily conditions of the spine, pelvis, lungs, heart, brain, and skin. Certain extremity injuries that are progressive, severe, or otherwise not amenable to a schedule award also belong here, including complex regional pain syndrome, failed joint replacements, and severe joint instability.⁴

Instead of assigning a percentage of loss, state the basis for the impairment classification and describe the claimant’s functional capabilities and limitations. The form asks for an impairment ranking and a narrative covering how long the worker can sit, stand, or walk, how much they can lift, and whether they have restrictions on bending, reaching, or repetitive motion. That functional picture is what the Board uses to calculate loss of wage-earning capacity under Section 15(3)(w).³

Non-schedule awards pay two-thirds of the difference between pre-injury average weekly wages and post-injury earning capacity. The statute caps total weeks based on the percentage of lost earning capacity, ranging from 225 weeks at 15 percent or less up to 525 weeks when loss exceeds 95 percent.³ The more thoroughly you document functional limitations, the better position the claimant is in when the Board sets that capacity.

How and When to Submit

The C-4.3 is not filed as a standalone document. Attach it to an electronically submitted CMS-1500 medical bill as the medical narrative rather than sending it to the Board separately.⁵ This electronic method replaced the older approach where C-4 series forms were sent independently.

Beyond filing with the Board, send the report promptly to the insurance carrier and to the claimant’s attorney or licensed representative. If the claimant has no representative, send a copy directly to the injured worker.¹ The form’s instructions warn that failing to submit promptly can delay treatment payments, hold up wage-loss benefits, force you into testimony, and put your Board authorization at risk.

Under 12 NYCRR 325-1.3, treating providers file medical reports at set intervals: within 48 hours of first treatment, within 15 days after that initial report, and for each follow-up visit thereafter at intervals no longer than 90 days. A separate filing obligation applies when a claimant reaches maximum medical improvement, and that report must include an opinion on whether any permanent impairment exists.⁶ The regulation does not attach an hour deadline to the MMI report the way it does to the initial treatment report, but the form’s instruction to submit “promptly” means a completed C-4.3 should not sit on your desk.

What Happens After You File

Once the Board receives the C-4.3, the opposing party gets a chance to review the impairment opinion. If the carrier agrees with your findings, the case can move toward a final award without a hearing. If not, the carrier submits conflicting medical evidence, often from an independent medical examination.⁷

When the disagreement is limited to whether the claimant has actually reached MMI, the parties may take medical testimony and the Board decides the question. When the conflict is about the degree of impairment or functional loss, both sides can present additional medical evidence. If no agreement is reached, the Board schedules a hearing where a Workers’ Compensation Law Judge takes testimony on medical and vocational factors and issues a decision on loss of wage-earning capacity.⁷

Mistakes That Delay the Process

The most frequent problem is mismatched identifiers. A WCB Case Number with a transposed digit, or a carrier name that doesn’t match Board records, can route the report to the wrong file entirely.

Incomplete clinical documentation is the other recurring issue. A schedule loss of use percentage without supporting range-of-motion measurements will almost certainly draw a challenge from the carrier. A non-schedule classification that describes the diagnosis but skips the functional-limitation narrative gives the Board nothing to work with when calculating wage-earning capacity. Treat the C-4.3 as a document that will be read by a judge, not just processed by a clerk, because if the carrier disputes the findings, that is exactly what happens.

Finally, forgetting to distribute copies creates its own delays. If the carrier never receives the report, the carrier cannot agree or disagree with it. If the claimant’s attorney is left out, the claimant cannot prepare for a hearing they may not know is coming.

1
New York Workers’ Compensation Board. Doctor’s Report of MMI/Permanent Partial Impairment
2
New York State Workers’ Compensation Board. Workers’ Compensation Guidelines for Determining Impairment
3
New York State Senate. New York Workers’ Compensation Code 15 – Schedule in Case of Disability
4
New York State Workers’ Compensation Board. Awards for Loss of Use or Permanent Disability
5
Workers’ Compensation Board. Workers’ Compensation Board All Common Forms
6
Law.Cornell.Edu. N.Y. Comp. Codes R. and Regs. Tit. 12 325-1.3 – Reports of Treating Providers
7
New York State Workers’ Compensation Board. Subject Number 046-472