Taxation of Social Security Disability Backpay
Large lump-sum payments of back payments of SSDI can bump your income up for the year in which you receive them, which can cause you to pay a bigger chunk of your backpay in taxes than you should have to. To avoid losing part of your backpay this way, you are allowed to apply the SSDI benefits owed from a prior year to prior tax returns, lowering your income for the year you receive the lump sum. You could amend your tax returns for two prior years to claim some of the income in those years instead of the current year.
Social Security sends beneficiaries a form called the SSA-1099 each year they receive benefits. If you're receiving this form for the first time, it should state in Box 3 the exact amount of your lump sum that was accrued during previous years. Each year will be listed separately alongside the total amount paid for that year. Rather than requiring you to file amended returns for those years, the IRS allows you to handle it all on your current tax return, using prior years' income amounts. This method is discussed in IRS Publication 915.
It provides a way to calculate how much of your lump sum payment is taxable.
the amended return and "915" methods may not produce the same results,
