You owe nothing unless you win your social security disability claim. Generally, if you win your SSI or SSDI claim, the fee is 25 percent of your backpay up to the government imposed maximum, which is currently set at $7,200. Because the fee comes out of your backpay, you do not have to write a check. The Social Security Administration (SSA) will automatically calculate your backpay and send the attorney fee directly to the firm. The remainder is then mailed directly to you by the SSA.