About 430,000 military households that are missing Social Security numbers in the Defense Enrollment Eligibility Reporting System could be forced to pay fines to the Internal Revenue Service if they don't update their information by January.

Troops were notified about the missing information through letters sent by DEERS starting Aug. 13. Social Security numbers are either missing or unverified for about 484,000 military dependents, Defense Department officials said.

The Pentagon is required to report healthcare coverage given to service members and their dependents as part of the Affordable Care Act beginning this year. But to do so, they need to have each dependent's SSN verified in the system, the letter said.

"The IRS will collect fees from individuals who don't have minimum essential coverage," it states. "Tricare verifies and reports minimal essential coverage status based on DEERS records."

Social Security numbers are not required for DEERS registration. For example, military child dependents often do not have their Social Security numbers in DEERS because their parents register them in the system as infants before the card is issued. Parents must return to DEERS later with the Social Security number to update the system -- a task that is often overlooked.

How to update your information in DEERS.

Fees for not holding the required minimum health care coverage depend on income and household size.

All Tricare enrolled active-duty service members and retirees meet the coverage minimums, provided all their dependents' Social Security numbers are up-to-date in DEERS. Those covered under purchased Reserve Select, Reserve Retiree and Tricare Young Adult also meet the requirement.

But some Tricare users don't meet the minimum coverage requirement and will face fines if they do not purchase additional coverage. Guard members and reservists who are receiving Tricare-provided line of duty care for an injury received during service do not meet the minimum through Tricare alone. Also, some dependent parents and parents-in-law receive Tricare as part of the Tricare Plus program, which allows them to use some military treatment facilities, but does not meet the minimum coverage requirements.

Tricare beneficiaries who had minimum essential coverage for any part of 2015 will be sent IRS Form 1095-C or 1095-B by Jan. 31, 2016, which will be needed to complete their 2015 tax returns, officials said.

Troops' mailing addresses, email addresses, phone numbers and the name and birth dates of dependents can be confirmed online. Social Security numbers must be added or verified in person at a military ID office. Military spouses can update the information in DEERS on their service members' behalf if they have a valid special Power of Attorney.

-- Amy Bushatz can be reached at amy.bushatz@military.com.