The IRS wants you to know: “Although most 2018 tax filers are still expected to get refunds, some taxpayers will unexpectedly owe additional tax when they file their returns.” (See the IRS news release on the subject at http://ow.ly/89EP30o4ruh.)

That’s good reason to do your taxes now, even if you are used to filing closer to April 15.

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The problem arose as a result of changes in withholding tables.

“The updated federal tax withholding tables, released in early 2018, largely reflected the lower tax rates and the increased standard deduction brought about by the new law. This generally meant taxpayers had less tax withheld in 2018 and saw more in their paychecks,” the release says.

“However, the withholding tables couldn’t fully factor in other changes, such as the suspension of dependency exemptions and reduced itemized deductions. As a result, some taxpayers could have paid too little tax during the year, if they did not submit a properly revised W-4 withholding form to their employer or increase their estimated tax payments.”

If you are affected, you might owe a penalty for underpayment of taxes.

However, the IRS anticipated underwithholding and issued temporary relief for 2018.

IRS Commissioner Chuck Rettig commented: “We realize(d) there were many changes that affected people last year, and this penalty waiver will help taxpayers who inadvertently didn’t have enough tax withheld.”

This is what you need to know.

“The IRS is generally waiving the penalty for any taxpayer who paid at least 85 percent of their total tax liability during the year through federal income tax withholding, quarterly estimated tax payments or a combination of the two,” the release says. “The usual percentage threshold is 90 percent to avoid a penalty.”

To determine if you qualify for the waiver, you’ll need IRS Form 2210.

Read the instructions first, since the form itself does not use the 85 percent figure.

In the instructions, you’ll find a reference to the special underpayment penalty waiver, as well as an “85 Percent Exception Worksheet” on Page 3.

Let me repeat: When you complete Form 2210, you’ll see a reference to a 90 percent figure (Part I line 5); however, the instructions to the form provide an “85 Percent Exception Worksheet” on Page 3 that takes you to the correct result.

You’ll find the instructions here: www.irs.gov/pub/irs-pdf/i2210.pdf, and the form here: www.irs.gov/pub/irs-pdf/f2210.pdf. You’ll need to file Form 2210 with your 2018 tax return to request the waiver.

Rettig also urged taxpayers to check their withholding now for 2019. Good advice. Here’s how to do that: On the IRS website, you’ll find a tool called “Paycheck Checkup” (www.irs.gov/paycheck-checkup).

I spent a few minutes exploring the tool. It’s easy to use and worth the effort to avoid too little being withheld for taxes. You’ll need your most recent pay stubs and most recent tax return.

Here are some additional resources: “Relief from Addition to Tax for Underpayment of Estimated Income Tax by an Individual,” IRS Notice 2019-11; IRS Publication 5307, “Tax Reform: Basics for Individuals and Families”; and IRS Publication 5318, “Tax Reform: What’s New for Your Business.” You can also go online to irs.gov/taxreform. The IRS toll-free number for general tax questions is (800) 829-1040.

We’ll talk more about taxes over the next few weeks. As always, do send in questions on this and other topics.

On another note, I’m thinking of my next book project. Would you read a book that discussed market insights and techniques to manage retirement portfolios? There are many books on the subject of retirement investing — this one would focus on what you need to know and do to create income for life, offset inflation and taxes, and potentially leave a legacy for your family and charity. I welcome your thoughts.

Julie Jason, JD, LLM, is an author and personal money manager at Jackson, Grant of Stamford, Conn. She welcomes questions and comments at readers@juliejason.com.