Free tool
SSDI back pay calculator
Disability claims take a long time, and benefits accrue while you wait. This estimates what has built up — including the two rules that reduce it.
Estimate your back pay
Nothing you enter here is sent anywhere. This runs entirely in your browser.
Find this on your Social Security statement at ssa.gov. If you don't know it, $1,580 is close to the national average.
Social Security calls this your onset date.
Leave this at today's date if your claim is still pending.
Estimated past-due benefits
$0
- Months of back pay
- 0
- Benefits begin
- —
- Representative's fee
- $0
- Estimated to you
- $0
This is an estimate for general information only, not a promise of benefits. Only the Social Security Administration can decide your claim and calculate your actual payment.
How the math works
Three dates decide your back pay, and two rules cut it down.
1. Your onset date starts the clock
Social Security establishes the date your condition began preventing substantial work. You propose a date on your application; the agency may accept it, move it, or reject it based on your medical records. Every calculation flows from whatever date they settle on.
2. Five months come off the front
SSDI has a mandatory five-full-month waiting period after the onset date. No benefits are payable during it, regardless of how severe the condition is. Claims involving ALS are the notable exception.
3. Retroactive benefits stop at twelve months
Even if your onset date was years ago, SSDI pays no more than twelve months of benefits before the date you filed. Someone who waited three years to apply loses the difference permanently. This is the single most expensive mistake in the process, and it's entirely avoidable.
4. Your entitlement date is whichever comes later
The calculator takes the later of onset-plus-five-months and application-date-minus-twelve-months. Benefits accrue from there until approval. Multiply by your monthly benefit amount and that's your past-due total.
5. The representative's fee comes out of it
If you used an attorney or accredited advocate, Social Security withholds 25% of past-due benefits or $9,200, whichever is less, and pays them directly. That cap has been unchanged since November 2024.
Common questions
What is SSDI back pay?
Back pay is the money that accumulated between the date you became entitled to benefits and the date Social Security actually approved your claim. Because decisions often take a year or more, back pay is frequently the largest single check a claimant receives.
Why is there a five-month waiting period?
Federal law imposes a five-full-month waiting period after your established onset date before SSDI benefits can begin. It applies to nearly every claim. The only common exception is amyotrophic lateral sclerosis, where the waiting period was eliminated.
How far back can benefits go?
For SSDI, retroactive benefits reach at most twelve months before the date you applied — and never earlier than five months after your onset date. That twelve-month cap is why filing sooner rather than later matters financially even when a claim seems weak.
How much does a representative take out of back pay?
Under the standard fee agreement process, the fee is 25% of past-due benefits or $9,200, whichever is less. Social Security withholds it from your back pay and pays the representative directly. A separate fee petition process can exceed the cap, but it requires approval from the judge on your case.
Is back pay paid all at once?
SSDI back pay is generally paid as a single lump sum. SSI back pay is usually split into installments when the amount is large. Many people receive both benefits, in which case the two are handled under different rules.
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