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The IRS has been warning filers all year to ensure they're withholding enough tax from their pay in order to avoid a surprise tax bill in 2019. Turns out, few people seem to be listening. At least that's the conclusion from a recent survey by Liberty Tax. The tax preparer polled 1,020 individuals online in September. About 70 percent of participants haven't checked their withholding — the income taxes deducted from their paychecks — in the last six months, Liberty Tax found. Nearly half of the polled individuals said they weren't concerned about whether they'd owe Uncle Sam next year. They should be however. "It's indicative of the population," said Brian Ashcraft, director of customer experience at Liberty Tax. "There has been so much tax talk and we get numb to it at some point in time."

The Tax Cuts and Jobs Act, which went into effect at the start of the year, slashed individual income tax rates, eliminated personal exemptions and roughly doubled the standard deduction. As a result, Treasury and the IRS made updates to the tax withholding tables. These are guidelines employers use along with Form W-4 to determine how much income tax workers should withhold from each paycheck. Nailing the right amount to withhold is an art: If you pay too much in taxes through the year, you will have made an interest free loan to the government and you'll get a refund in the spring. Withhold too little, and you'll be on the hook for additional taxes in April. Here's what you can do, now that the year is nearly over.

Tax cuts

The Internal Revenue Services offices in Washington, D.C. Adam Jeffery | CNBC

Throughout this year, the IRS has repeatedly reminded taxpayers to check their withholding at work — or in their pensions if they're retired — to account for changes to the tax law. Nevertheless, the Government Accountability Office estimates that about 2 in 10 taxpayers will owe the IRS in 2019. That's equal to about 30 million people. Though checking your withholding is generally a good practice, these payers ought to pay especially close attention: Filers who itemize: Prior to the new tax law, it may have made sense to withhold less from your pay if you itemized deductions. That may no longer be the case now that the standard deduction has nearly doubled to $12,000 for singles and $24,000 for married couples filing jointly. Those who itemized in the past may no longer do so going forward, so they may need to revisit their withholding. Households with dependents: Under the old law, it may have made sense to withhold less in taxes if you had dependents. Now, personal and dependent exemptions are out, so these filers should review their paystubs to ensure that they're not underwithheld. Retirees: Just because you're no longer working, doesn't mean that you still won't owe. You can use Form W-4V to withhold a flat rate from your Social Security check or Form W-4P to withhold from your pension.

Small refunds, big bills

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