How can I prove my income to become a citizen in the US?

While filing required tax returns and paying taxes that are due are addressed in the application process to become a naturalized citizen, that process does not require submission of documentary evidence of one's income. The information and documentation needed for immigration application processes can be complex, and failing to provide a full set of required supporting documentation can cause substantial delays or even more harsh consequences. It would be wise for you to consult with an immigration attorney who, after learning all of the relevant information, could advise about eligibilities, options and strategies (including identification of needed documentation) to attain your goals, and who then could offer legal representation in the often complex application process.