Make sure you have all your tax preparation documents
All your W-2s
Form SSA-1099 if you received Social Security benefits
Form 1095-A to report information from the government Marketplace from which you purchased health coverage
Various 1099s to report income such as cancellation of debt (1099-C), dividends (1099-D), interest (1099-INT), and nonemployee compensation paid to independent contractors (1099-MISC). Note: Form 1099-B, which reports gains and losses on securities transactions, is not due to you until February 15, 2018.
Various 1098s reporting mortgage interest (1098), student loan interest (1098-E) and tuition payments (1098-T)
Form W-2Gs for certain gambling winnings
Schedule K-1s from entities in which you have an ownership interest (e.g., S corporations, partnerships, limited liability companies, trusts or estates). Note: You may not have received them yet; they are due by the first March 15 following the end of the partnership's tax year; check with the entity if one doesn't arrive.