For some taxpayers who face an unexpected tax bill, another hit could come with it: no way to pay what's owed by the April 15 due date. With returns being prepared for the first time under new tax law, some people are getting caught flat-footed by owing money to Uncle Sam after past refunds or owing more than anticipated — despite lower marginal income tax rates across the board. The reasons for the surprise bills vary, although one contributing culprit is the reduced payroll withholding rates applied in 2018. In simple terms, this means the amount withheld from worker paychecks wasn't enough to cover their tax liability for the year. Other factors include the elimination of personal exemptions and the limited deductions available to itemizers.

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If you think (or know) you'll be unable to pay your 2018 tax bill by April 15, experts say it's important to avoid panicking and to file your return anyway. "Even if you can't pay in full, you still want to file," said Jeff Warnkin, a certified financial planner and CPA with JL Smith Group in Avon, Ohio. "You don't want to be subject to a late-filing penalty." That failure-to-file levy is pretty steep: 5 percent of the unpaid balance for each month it's late, up to a maximum of 25 percent of the amount due. So if you owe $1,000 and don't file your return, that fee alone could reach $250 after five months. By comparison, if you file your return even if you cannot pay the full amount due, the penalty is lower: generally 0.5 percent per month, up to a maximum 25 percent, of your unpaid taxes. So for that hypothetical $1,000 owed, if you paid none of it for five months, you'd accrue 2.5 percent from that penalty, or $25.