The IRS urges taxpayers to use its online refund-tracking feature to determine why they have not received their refund check. The “Where’s My Refund?” feature at www.irs.gov can also help taxpayers solve problems, such as incorrect addresses.: http://www.irs.gov/individuals/article/0,,id=96596,00.html.

For example, the IRS has said 115,744 child tax credit checks worth more than $50 million were undeliverable after the service issued them July and August. Taxpayers had until Dec. 5 to claim their undelivered child tax credit checks. After that, taxpayers cannot claim the checks until they file their tax returns next year (The IRS issued nearly 24 million checks worth more than $14 billion in an advance of the increased child tax credit.)

To use this tracking site, taxpayers enter information including their Social Security numbers and their filing status, such as single or married filing jointly, the refund amount shown on their tax return and the number of exemptions shown on their tax return.

When the information is submitted online, taxpayers can view Web pages that show the status of their refunds or child tax credit. In many cases, they also get instructions about solving problems. If the IRS has the wrong address, taxpayers must update the address information before the IRS can reissue the checks.