Independent guide · not the SSA

Tool · SSDI back pay

SSDI back pay calculator

Back pay is the SSDI money for months before your first regular payment. Enter when your disability began, when you applied and when the decision came, plus the monthly amount from your SSA letter.

Month your disability began

MonthJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecemberYear2027202620252024202320222021202020192018201720162015

The date SSA finds, often called the onset date.

It began on the 1st day of that month

Month you applied

MonthJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecemberYear2027202620252024202320222021202020192018201720162015

Month of the decision letter

MonthJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecemberYear2027202620252024202320222021202020192018201720162015

Your monthly SSDI amount (from your SSA letter) Diagnosed with ALS (no waiting period) A representative helped me under a fee agreement

The rules behind the estimate

5 months

Waiting period. SSDI is paid from the sixth full month after the date SSA finds your disability began.

12 months

Before you applied. SSDI can pay for up to 12 months before the month you applied, if you were disabled then.

25% or $9,200

Representative fee cap. Under a fee agreement, the fee is the lower of 25% of past-due benefits or $9,200 (decisions since Nov. 30, 2024).

SSI back pay follows other rules: SSI can only start the month after you apply, and large SSI back pay (3 or more times the monthly amount) is paid in up to 3 installments, 6 months apart. No waiting period applies to people with ALS whose SSDI was allowed on or after July 23, 2020.

This is an estimate only; only SSA decides your back pay. It does not add yearly cost-of-living raises and does not subtract other offsets, such as workers' compensation.

Free tools

Denied? Appeal stepsDeadlines and levelsMy payment dateSSI and SSDI, 2026–2027Working on SSDISGA and trial work check

Questions people ask

How far back does SSDI back pay go?

Up to 12 months before the month you applied, but never before the end of the 5-month waiting period that starts when your disability began.

Is the representative fee taken out of back pay?

Under a fee agreement that SSA accepts, SSA limits the fee to the lower of 25% of past-due benefits or $9,200 for decisions since Nov. 30, 2024.

Where do I find my monthly SSDI amount?

On your SSA award letter or in your my Social Security account. This guide does not know your amount, so type it in.

Independent guide · not the SSA. Green Tips 1 US is a private guide. We are not the Social Security Administration, we are not part of it, and we do not take applications.

Sources: 20 CFR 404.315 (5-month waiting period; ALS); 20 CFR 404.621 (up to 12 months before the application); 20 CFR 416.335 and 416.545 (SSI start month and installments); SSA, Fee Agreements (fee cap of $9,200 since Nov. 30, 2024); SSA, How Does Someone Become Eligible? (disability benefits). Official site, typed by hand: ssa.gov. Read in October 2026; data dates as noted.