WASHINGTON — While the federal income tax-filing deadline has passed for most people, there are some taxpayers still facing tax-related issues. This includes people who still haven’t filed, people who haven’t paid their taxes or those who are waiting for their tax refund.

The IRS offers these tips for handling some typical after-tax-day issues:

Didn’t file by April 18?

There is no penalty for filing a late return after the tax deadline if a refund is due. Penalties and interest only accrue on unfiled returns if taxes are not paid by April 18. The IRS provided taxpayers an additional day to file and pay their taxes following system issues that surfaced early on the April 17 tax deadline. Anyone who did not file and owes tax should file a return as soon as they can and pay as much as possible to reduce penalties and interest. For those who qualify, IRS Free File is still available on IRS.gov through Oct. 15 to prepare and file returns electronically.

Filing soon is especially important because the late-filing penalty on unpaid taxes adds up quickly. Ordinarily, this penalty, also known as the failure-to-file penalty, is usually 5 percent for each month or part of a month that a return is late.

But if a return is filed more than 60 days after the April due date, the minimum penalty is either $210 or 100 percent of the unpaid tax, whichever is less. This means that if the tax due is $210 or less, the penalty is equal to the tax amount due. If the tax due is more than $210, the penalty is at least $210.

In some instances, a taxpayer filing after the deadline may qualify for penalty relief. If there is a good reason for filing late, be sure to attach an explanation to the return.

Alternatively, taxpayers who have a history of filing and paying on time often qualify for penalty relief. A taxpayer will usually qualify for this relief if they haven’t been assessed penalties for the past three years and meet other requirements. For more information, see the first-time penalty abatement page on IRS.gov.

“Where’s My Refund?”

The “Where’s My Refund?” tool is available on IRS.gov, IRS2Go and by phone at 800-829-1954. To use this tool, taxpayers need the primary Social Security number on the return, the filing status (Single, Married Filing Jointly, etc.) and the expected refund amount. The tool updates once daily, usually overnight, so checking more frequently will not yield different results.

Changing withholding?

Because of the far-reaching tax changes taking effect this year, the IRS urges all employees, including those with other sources of income, to perform a paycheck checkup now. Doing so now will help avoid an unexpected year-end tax bill and possibly a penalty. The easiest way to do that is to use the newly-revised Withholding Calculator, available on IRS.gov.

Owe taxes or need to make a payment?

Taxpayers who owe taxes can view their balance, pay with IRS Direct Pay, by debit or credit card or apply online for a payment plan, including an installment agreement. Before accessing their tax account online, users must authenticate their identity through the Secure Access process. Several other electronic payment options are available on IRS.gov/payments. They are secure and easy to use. Taxpayers paying electronically receive immediate confirmation when they submit their payment. Also, with Direct Pay and EFTPS, taxpayers can opt in to receive email notifications about their payments.

Need to fix an error on a return?

After filing their return, taxpayers may determine that they made an error or omitted something from their return. Usually an amended return is not necessary if a taxpayer makes a math error or neglects to attach a required form or schedule. Normally the IRS will correct the math error and notify the taxpayer by mail. Similarly, the agency will send a letter requesting any missing forms or schedules. Taxpayers can use the Interactive Tax Assistant — Should I File an Amended Return?— to help determine if they should file an amended return to correct an error or make other changes to their return.

Form 1040X, Amended U.S. Individual Income Tax Return, must be filed by paper and is available on IRS.gov/forms at any time. Those expecting a refund from their original return, should not file an amended return before the original return has been processed. File an amended tax return to change the filing status or to correct income, deductions or credits shown on the originally-filed tax return. Use “Where’s My Amended Return?” tool to track the status of an amended return. Normally, status updates are available starting three weeks after the amended return is filed. Allow up to 16 weeks for processing.

Need help responding to an IRS notice or letter?

An IRS notice or letter will explain the reason for the contact and give instructions on how to handle the issue. Most questions can be answered by visiting “Understanding Your Notice or IRS Letter” on IRS.gov. Taxpayers can call the phone number provided in the notice if they still have questions. If the issue can’t be resolved with the IRS through normal channels, contact the local Taxpayer Advocate Serviceoffice or call 877-777-4778.

Taxpayer Bill of Rights

Taxpayers have fundamental rights under the law. The Taxpayer Bill of Rights presents these rights in 10 categories. These rights protect taxpayers when they interact with the IRS. Publication 1, Your Rights as a Taxpayer, highlights these rights and the agency’s obligations to protect them.

Watch out for scams

The IRS will never make an initial, unsolicited contact via email, text or social media on filing, payment or refund issues. The IRS initiates most contacts through regular mail delivered by the United States Postal Service. Any email that appears to be from the IRS about a refund or tax problem is probably an attempt by scammers to steal personal or financial information. Forward the e-mail to phishing@irs.gov.