How To Write Apt Unit Address On Irs Form . Complete and sign part i of form 8609 and make copies of the form. Taxpayer information (name, address, taxpayer identification number, and phone number); Form 1040V Payment Voucher from formupack.com Write it in one single line, for example: According to the usps, the standard way for writing an address is on three lines: How to complete forms 2848 and 8821.