These additional schedules and forms add time and complexity to a tax return. This is not an inclusive list, but I've listed the most common ones.
Schedule A: Itemized Deductions
Schedule B: Interest and Ordinary Dividends
Schedule C: Profit or Loss From Business (sole proprietors/gig workers)
Schedule D: Capital Gains and Losses (especially stock trading)
Schedule E: Supplemental Income and Loss (rentals)
Schedule F: Profit or Loss From Farming
Schedule H: Household Employment Taxes
W-2G: Gambling Winnings
K-1: Complicated K-1's (other states, gas & oil)
1098-T: Tuition Expenses
1098-C: Cancellation of Debt
Credits for Child and Dependent Care
Alimony Paid (divorce or separation agreements executed by 12/31/18)
FBAR: Report of Foreign Bank & Financial Accounts
State Income tax returns
Many complicated returns trigger Estimated Tax payments. Please bring information about amount and date paid for any payments made on EFTPS or by mail with 1040-ES coupons.