What is Backup Withholding?
Backup withholding is a flat rate a payer must hold back from certain payments when your taxpayer info is missing or flagged.
How it works
If you don't give a correct TIN on a W-9, or the IRS notifies a payer that you've under-reported, the payer withholds a set percentage (currently 24%) from payments like interest, dividends, and contractor pay, and sends it to the IRS as a prepayment of your tax.
A quick example
What people get wrong
Backup withholding is almost always avoidable — just make sure the name and TIN on your W-9 exactly match IRS records. A typo is the usual culprit.