A few things to bring:
Last year's tax return (if we didn't prepare it)
W-2 forms
1099's of any kind (misc. income, interest income, etc.)
Investment, Mutual fund, and Stock Trade Statements
K-1 schedules from Partnerships, LLC's, S-corporations
Retirement plan contributions and/or withdrawals (1099-R)
1098 statement(s) from mortgages
Medical expenses (including Rx, co-pays, mileage)
1095 Affordable Care Act (health insurance) notices
HSA and health insurance information
Charitable contributions (including cash, non-cash, and mileage)
Dependent info (SSN, DOB, relationship, # of months spent at home)
Tuition, fees, and required course materials (bring 1098-T)
Alimony paid or received (do not include child support)
Sales tax paid on vehicles or other major purchases
Settlement HUD's on sale and/or purchase of real estate or houses
Costs of windows, insulation, furnace, water heaters qualifying for credit
Moving expenses, job hunting expenses
Anything else you think might help...
If you have a business or rental property:
Income received (include 1099-K, 1099-Misc)
Expenses related to the business or income
Mileage (business use of vehicles)
Home office and total sq. footage, utilities paid, cell phone costs