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Unhappy with your 2018 tax return? Now's the time to correct course to avoid the same outcome next year. This spring marks the first time that taxpayers are filing under the Tax Cuts and Jobs Act, an overhaul of the tax code that went into effect in 2018. The new tax law roughly doubled the standard deduction to $12,000 for singles and $24,000 for married joint filers, eliminated personal exemptions and limited certain itemized deductions.

Tax refunds, which were off to a slow start early in the season, are also approaching parity with last year's figures. The average tax refund as of March 22 is $2,915, according to the IRS. That's just $10 — or 0.3 percent — down from last year. Refunds aside, accountants are still finding themselves the bearers of bad news to some filers who found themselves owing this spring. "We've seen people who never owed and now they owe," said Dan Herron, CPA and partner at Better Business Financial Services in San Luis Obispo, California. "I don't think anyone had an understanding of what the tax reform dynamic would entail," he said.

Hitting a snag

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Accountants identified a few areas of the new tax law that tripped up some of their clients: Withholding: The Treasury Department and the IRS introduced new withholding tables last spring to reflect the new tax code. Employers use these tables as a guideline, along with your Form W-4, to calculate the amount of income tax to withhold from your pay. If you withhold less in taxes, you take home more money. But you may owe the IRS next year if you withhold too little.

Withhold too much, and your pay will go down. But you'll probably get a refund next year. The IRS warned taxpayers that they needed to revisit their withholding in 2018, especially due to lower tax rates, the elimination of personal exemptions and changes to itemized deductions. "When the new tables rolled out, the withholdings went down across the board," said Sharif Muhammad, CPA and certified financial planner at Unlimited Financial Services in Somerset, New Jersey. "People don't pay attention to their paystubs." Unreimbursed employee expenses: This now-suspended tax break is part of a group of miscellaneous itemized deductions, which you were only able to claim to the extent they exceed 2 percent of your adjusted gross income. The inability to deduct unreimbursed employee costs hit clients in a range of industries, from traveling salesmen to construction workers and pipefitters, CPAs said. More from Personal Finance

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What the Wyden-proposed tax on unrealized gains means for you "It's not unusual to see a pipeliner with $30,000 to $40,000 in unreimbursed employee expenses," said Jeffrey A. Porter, CPA at Porter & Associates in Huntington, West Virginia. "They travel in a three- to four-state area, and those guys are getting hit hard." $10,000 cap on state and local income tax deduction: Clients on the coasts, particularly in high-tax states such as New Jersey and California, aren't able to deduct as much of their state and local tax burden. The top three counties with the highest average property taxes were Westchester County, New York ($17,392); Rockland County, New York ($12,925); and Marin County, California ($12,242), according to ATTOM Data Solutions. In all, nine counties have an average property tax bill exceeding $10,000, ATTOM found. "The whole game of prepaying your real estate taxes and claiming a deduction doesn't pay anymore," said Herron.

Do it right in 2019

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