can I apply citizenship if I didn't file tax because I was retired and had no income?

Hello. Good question. When filing for naturalization, it is very important to review all of the facts and circumstances of each particular case. No two cases are exactly the same. Tax returns are helpful to prove certain elements in a naturalization case. If you did not need to file, you must prove those elements in other ways. The naturalization instructions recognize this fact in stating that tax returns are not required in every case. These issues must be addressed properly in your application. You are highly encouraged to consult with an experienced immigration lawyer prior to filing. Good luck!