US Internal Revenue Code Section 3402 Income Tax Withholding at Source (26 USC 3402) 3402f3-4-certificate-effect: Give effect to a first certificate from the next payroll period and a replacement certificate by the first period ending at least thirty days after receipt, with the employer free to act sooner

What does 3402f3-4-certificate-effect require?

A certificate furnished when none is in effect takes effect with the first payroll period that ends, or the first non-period payment made, on or after the day the employer receives it. A certificate replacing one in effect takes effect from the first payroll period ending (or first non-period payment) on or after the thirtieth day after it is furnished, though the employer may elect to apply it from any payment made after receipt; a certificate furnished for the next calendar year cannot take effect for payments in the current year. A certificate that has taken effect stays in force with that employer until another takes effect. The form and contents are as the Secretary prescribes.