​This report provides results of a test conducted to address stakeholder and respondent concerns about the prominent mandatory message “Your Response Is Required By Law” used on American Community Survey envelope mailing materials.  The test, conducted in May 2015, removed the mandatory message from two mailing envelopes, the Initial Mailing Package Envelope and the Paper Questionnaire Mailing Package envelope.  The results of the test show how the message removal affected return rates and final response rates. The report also provides insight into the impact of the message removal on “hard-to-count” populations, cost estimates, and survey reliability estimates.