The Form W-8BEN must be kept up to date. If it is not, the foreign person may find that the agent has withheld tax on the income.
Generally, a Form W-8 provided without a US Taxpayer Identification Number (TIN) will remain in effect starting on the date the form is signed and ending on the last day of the third succeeding calendar year unless a change in circumstances makes any information on the form incorrect. For example, a Form W-8BEN signed on September 30, 2021, remains valid through December 31, 2024. A Form W-8BEN with a US TIN will remain in effect until a change of circumstances makes any information on the form incorrect, provided that the withholding agent reports on Form 1042-S at least one payment annually to the beneficial owner.