“I would never take continuing ed during tax season,” he said. “But we’re all going for three hours on Friday — it’s on nothing but the Section 199A deduction.”

Janet Lee Krochman, an accountant from Costa Mesa, Calif., said she was also still learning about how the rule worked.

“We weren’t expecting to get 180 pages of regulations on the 18th of January, 10 days to the opening of filing season,” she said.

There have been other complexities. Tax filers in places that require their state and federal returns to mirror each other — for example, if they take the standard deduction on their federal return, they must do the same on their state return — may end up owing more to their states than in the past. The reason: Standard deductions in states like Kansas, Virginia and Maryland are on the lower end. (Lawmakers in states including Virginia and Maryland have voted to raise their standard deductions to help compensate.)

As a result, tax pros in these states are suggesting running multiple sets of calculations. It may be worth sacrificing the larger federal standard deduction to itemize on the state level and get a bigger return there.

“If you are single with significant state income or real estate taxes, by choosing to deduct the lower amount of itemized deductions on your federal return you may reduce your overall federal and state tax due to the increased deduction on your Kansas return,” said Julie Welch, an accountant in Leawood, Kan. “It pays to run the calculation.”

Despite the confusion, some accountants have had the pleasure of delivering good news. Conor Barnes, an accountant at Egan Tax & Books in New York, prepares returns for many renters who typically don’t have enough individual deductions to itemize their returns. Instead, those filers take the standard deduction, which has doubled.