For Form 1040 returns, mailing addresses are grouped by which geographic area?

For Form 1040 returns, mailing addresses are organized based on the state in which the taxpayer resides. The Internal Revenue Service (IRS) categorizes correspondence and processes tax returns by state to streamline workflow and manage regional operations more efficiently. Each state has a specific mailing address designated for the submission of tax returns, which helps in directing returns to the appropriate IRS processing center based on geographic location.

This approach ensures that returns are handled by the IRS staff familiar with the tax laws and regulations relevant to that particular state, which can vary significantly across the country. The state serves as the primary geographic division for this purpose rather than smaller divisions like city, municipality, or county, which could lead to confusion due to overlapping addresses and varying rules within states.