The tax preparers at H&R Block had to take a new class before their busy season started this year: empathy training.

They listened to a mock exchange between an employee and a customer whose refund would not just shrink but disappear. The fictitious client had received a $1,500 refund last year, but this year would owe $575.

The playacting was prescient. The tax overhaul that took effect last year promised relief, but now that returns are being filed, some people are baffled. They’re getting smaller refunds — or sometimes having to write a check — even though nothing in their situation seems to have changed.

The average refund among early filers was down 8.4 percent, according to the Internal Revenue Service. The smaller checks, in some cases, stem from the loss of certain deductions. For others, it’s because less money is being withheld from their paychecks. The I.R.S., in trying to more closely match the amount held out of paychecks with the amount that taxpayers will owe, changed its withholding tables.

“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.

“Now that the standard deduction is higher than what it has been,” Ms. Barnes said, “people without mortgage interest and real estate taxes are seeing a tax benefit they haven’t seen in prior years.”

She also works with a lot of freelance workers, including photographers, who didn’t realize they would receive a nice tax benefit from the new qualified business income deduction.