Final answer:
The backup withholding rate in 2018 was 24%. It is a tax withholding required for payments like interest and dividends if specific conditions aren't met by the payee, such as providing a correct TIN.
Step-by-step explanation:
The percentage for backup withholding in 2018 was 24%. Backup withholding is a form of tax withholding on income for federal tax purposes. It is required from payments that are not usually subject to withholding, such as interest, dividends, and certain other payments to independent contractors.
The payer must withhold tax from such payments if the payee fails to provide their taxpayer identification number (TIN) correctly or if the IRS notifies the payer that the payee is subject to backup withholding.