Contractors and freelancers often file a W-9 form with the company paying them in order to pay taxes on the income they earn. Employers and the Internal Revenue Service need to certify the worker's taxpayer identification number and biographical data such as address. The W-9 instructions don't mention the allowance of a post office box, but the form labels suggest using only a physical street address.
Provide an Address
The address line on the W-9 includes the parenthetical instructions of "number, street, and apt. or suite no." and suggests that the IRS only wants physical street addresses. Instructions at the bottom of the form make no specific mention of the address requirements, but the IRS has made stipulations on other common tax forms regarding the use of post office boxes. On the income tax reporting form 1040A, the IRS states that an individual should only use a post office box if the physical address cannot receive mail. Employees should ultimately use a street address rather than a post office box to avoid potential processing problems.