Itu2019s technically against the law to do so, though odds are you will not be prosecuted for it.They will send you several duplicate / follow up mailings. Then they will send someone to your house, multiple times, to ask you the questions in person assuming that you are too illiterate to fill out the form on your own.Then they will use your neighbors and other sources of data that are in some ways more intrusive to try to get the simple answers you could have given them.Ultimately, all of this extra effort will cost you and every other taxpayer more money when you could have just obeyed the law and filled out the frigging form like an ordinary responsible citizen.If you do succeed in hiding out, your state may get less representation in Congress, your vote for the presidency may be weakened, and your state and town will be eligible for less money.Specifically, you may lose money for:MedicaidFood StampsMedicare Part BHighway PlanningCollege Grants and ScholarshipsSchool lunches and Title I assistance to schoolsWelfareHead StartPublic TransportationFoster and Child CareHousingUnemployment AssistanceCommunity DevelopmentSubstance abuse prevention and Opioid crisis fundingCareer and Technical EducationWildlife PreservationFormula grants for rural areas and Rural Rental Assistanceand many, many, many more.In short, not filling out the form is illegal, selfish, and stupid.Source:Hotchkiss, M. and Phelan, J. Uses of Census Bureau Data in Federal Funds Distribution. U.S. Department of Commerce Economics & Statistics Administration, September, 2017.