Guide · updated 2026-07-30
Your SSA Award Letter, Decoded — SSDI Amounts, Back Pay & Dates
What each line of a Social Security disability award letter means: the established onset date, the five-month waiting period, your monthly benefit before deductions, the back-pay computation, and when Medicare eligibility begins — in plain, verifiable language.
The established onset date (EOD)
SSA's decision sets an established onset date — when the evidence shows your disability began. It may differ from the date you claimed. Every other date on the letter flows from it: your waiting period, your first payable month, and your back pay.
The five-month waiting period
SSDI entitlement begins the sixth full month after the onset date (waived for ALS approvals on or after July 23, 2020). If your onset was June 5, your first entitled month is December — the letter's 'date of entitlement' reflects exactly this arithmetic.
Your monthly amount
The benefit equals your Primary Insurance Amount — the bend-point formula applied to your indexed earnings history — not a needs-based figure and not affected by household income. The letter shows the gross amount; Medicare premiums (once eligible) and any workers'-compensation offset come out afterward.
Back pay on the letter
Past-due benefits cover the months from entitlement through the decision, and retroactive benefits can reach up to 12 months before your application date (20 CFR 404.621) when the onset supports it. The letter itemizes these months; attorney fees, if any, are deducted from past-due benefits under SSA's fee-agreement cap before you're paid.
What to verify, and where
Check the onset date against your medical timeline and the monthly amount against your Social Security statement's disability estimate at ssa.gov/myaccount. Only SSA determines benefits; this page explains the document so the numbers aren't a mystery.
Official sources for this guide
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