Prices for the second ounce of domestic letters and postcards would increase by 1¢ and 1-ounce international letters by 5¢, under a new rate schedule announced by the United States Postal Service Jan. 15.

The first-class stamp would remain at 49¢ under the filing with the Postal Regulatory Commission.

If endorsed by the commission, the new rates would go into effect April 26.

The filing would raise overall postal revenues by $900 million a year, and by $400 million in the current fiscal year.

The Postal Service is allowed an annual rate increase based on the consumer price index. The new filing is based on a 1.966 percent increase in the index.

If mailers fight this proposed increase as vigorously as they have opposed other increases, they may challenge the fact the the Postal Service Board of Governors lacks a legal quorum because Congress has failed to fill vacancies on the board.

The fact that the basic letter rate was not changed might also reflect the fact that the emergency rate increase that produced the 49¢ stamp is being challenged in the federal courts.

Prices for the second ounce would go to 22¢, from 21¢; postcards would increase to 35¢, from 34¢; and international letters would cost $1.20 instead of the current $1.15.

“Today’s action is the latest in a series of steps the Postal Service has taken as part of a comprehensive approach to financial stability,” the agency said in a news release.