​Since the implementation of the American Community Survey (ACS) in 2005, the mail contact strategy has undergone several changes and enhancements based on the results from various tests. However, during that time, one feature that has largely not been tested is the timing of the mailings. The 2024 ACS Mailout Timing Test tested small changes to the timing of two of the mailings—the Due Date Letter and the Computer Assisted Personal Interviewing Internet Letter.​