Members of the military have a lot to navigate when it comes to filing their taxes. Servicemembers are entitled to some unique tax breaks under the tax code, which can make their tax returns more complicated than the average filer. And when they’re on a tour of duty outside of the United States or in a combat zone, they are automatically granted extensions to file their returns.

But this year, military members could jeopardize important tax credits if they delay obtaining a Social Security number (SSN) or individual taxpayer identification number (ITIN). Taxpayers and their dependents need to have tax identification numbers, either SSNs or ITINs by the filing deadline (including extensions), to claim certain tax credits. Previously, taxpayers could file late or amend returns to claim credits after the tax filing deadline.

The Protecting Americans from Tax Hikes (PATH) Act implemented new rules about eligibility for the child tax credit (CTC), American opportunity credit (AOC) and the earned income tax credit (EITC). Taxpayers and qualifying children now must have valid taxpayer identification numbers by the due date of the return (including extensions) in order to claim the CTC or AOC. And taxpayers and qualifying children must all have SSNs eligible for work by the due date of the return (including extensions) to claim the EITC.

There is no exception for servicemembers serving in the United States. For those serving outside of the U.S., who are eligible for an automatic extension to June 15, the SSN/ITIN requirement must generally be met by the automatic extension due date (or by the additional extension date, if applicable).

Taxpayers who must obtain SSNs for newborn children will benefit by starting the process as soon as possible to make sure they meet requirements by the applicable due date (including extensions) to claim the EITC when they file. Parents of U.S. children born abroad should allow for extra time to get SSNs. Taxpayers may want to request an additional extension if needed to allow more time to get SSNs.

For more information, taxpayers can learn more from the Tax Institute’s Timing is everything: The date taxpayers get an SSN or ITIN now affects whether they’re eligible for refundable tax credits.