More than 19,000 Washington car owners have been mailed license tag renewal forms that failed to credit them with payments for traffic tickets and mistakenly told them to pay the fines a second time, the D.C. Transportation Department reported yesterday.

Corrected statements and letters of apology will be mailed to all the affected motorists early next week, transportation director Thomas M. Downs said.

"We made a mistake in the way the computer program was put together," he said.

Under city regulations, all car owners must pay all outstanding parking and traffic fines before they car get 1982 tag renewal stickers. About 69,000 of the city's 300,000 car owners had records showing unpaid tickets and were sent special five-part forms requiring full fine payments before the stickers would be sent.

City car owners owe an estimated $3 million to $4 million in overdue fines, according to Robert Thompson, assistant transportation director for motor vehicle services.

Thompson said most of the 19,000 who got incorrect notices had paid the basic amount of their fines close to or after the 15-day deadline for payment shown on the traffic tickets. For payments after that deadline, the fines automatically double.

In such cases, because of a programming error, the computer failed to credit the basic payments and, adding insult to injury, added the late-payment penalty to the amount purportedly owed.

The new mailing will show the amount actually owed, deducting any payments already made, and will provide details of the transaction, Thompson said. It will instruct car owners to send the new statement to the city along with the original five-part renewal form and any payment still due.

Downs said any car owner who mistakenly overpaid his past fines as a result of the initial mailing will be sent a refund check.

Since the list of overdue tickets was compiled in December, payments of fines made by car owners since then were not reflected in the initial mailing of tag renewal forms, Thompson said. While he said he regrets inconvenience to those people, he said the department issued a public warning at the time that outstanding tickets would create tag-renewal problems. Maryland has adopted a similar enforcement program.

Thompson said his agency detected the problem soon after it mailed the renewal forms last week. Many people showed up to complain, some carrying canceled checks to prove they had paid their fines.