Understanding Mailing Names and Addresses for 1099 Suppliers
Review the mailing name and the address of each supplier for whom you generate a 1099 return. If the supplier's mailing name is not the same as the supplier's legal name (for example, the supplier is a sole proprietorship), add the legal name on an additional line in the Who's Who program (P0111).
The IRS limits addresses on 1099 returns to three lines (a maximum of 40 characters per line), consisting of name (line 1), street address (line 2), and city, state, and ZIP code (line 3). You cannot have a mailing address that contains more than one line for a street address.
When you must use a legal name in addition to a mailing name, the IRS allows four lines, as follows:
Legal name
Mailing name
Street
City, state, ZIP code (postal code)