Not sure if all the changes due to the Tax Cuts and Jobs Act have left you short-changing your income tax withholding? If you failed to withhold sufficient taxes from your pay in 2018, the IRS might grant you some forgiveness.

The tax agency said on Wednesday it would waive the penalty for taxpayers who paid at least 85 percent of their tax liability for 2018. Normally, in order to avoid a penalty for underpayment, you have to pay at least 90 percent of what you owe for the tax year in question or 100 percent of the tax liability from the prior year (110 percent if your adjusted gross income on that year's return exceeded $150,000).

The IRS has been reminding taxpayers to review their W-4 throughout 2018, asking them to ensure that they are withholding sufficient taxes from their pay.

That's because the Treasury Department and the IRS updated their withholding tables to reflect the changes from the new Tax Cuts and Jobs Act. The overhaul of the tax code slashed individual income tax rates, doubled the standard deduction and eliminated personal exemptions.

You should also know that if you paid less than 85 percent of the liability owed — the minimum threshold for 2018 — you will still be on the hook for the penalty. However, if you do qualify for the relief (meaning you paid at least 85%), you'll need to complete Form 2210, titled "Underpayment of Estimated Tax," and make note of the waiver on the form.

The withholding tables are guidelines your employer follows in order to deduct the appropriate amount of income taxes from your paycheck. You can also use your W-4 to tailor the taxes withheld from your pay. If not enough is withheld, you'll owe money come tax time. Pay too much, and you end up with a large refund. Ideally you want to come in as close to zero as possible on either side of owing or over-withholding.

Nearly three-quarters of taxpayers withheld too much in 2018 and, as a result, will receive a refund this year. On the flip-side, 21 percent of taxpayers — or about 30 million people — aren't withholding enough taxes, according to a report by the Government Accountability Office.

Before 2019, 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. Because of the new tax law, many of those who itemized in the past will no longer be able to do so going forward — one reason to revisit your withholding.

Under the old law, it may have also made sense to withhold less in taxes if you had dependents. Now, personal and dependent exemptions are out, so these filers should review their pay stub to ensure that they're not under-withheld.

If you've retired, 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. Otherwise, you should look into making quarterly estimated tax payments to avoid underpayment penalties.

The IRS has a withholding calculator to help taxpayers figure out how much to have deducted from each paycheck and help you estimate your 2019 income and compare it to your current withholding. To get started, you'll need a copy of your most recent pay stub and tax return. You can also cross-check that number with your CPA or tax preparer to make sure you are on the right track.