It's time to stock up on Forever stamps.
The cost of mailing a letter will go up a penny, to 42 cents, on May 12.
But the Forever stamps will still be valid for first-class postage after that. And they can be bought for 41 cents until the new rates take place, postal officials said.
The post office has sold 5-billion Forever stamps since they were introduced in April and it plans to have an additional 5-billion in stock to meet the expected demand before the May price change, the agency said.
Postage rates last went up in May 2007, with a first-class stamp jumping 2 cents to the current 41-cent rate.
In the past, raising postage rates was a complex procedure involving hearings before the independent Postal Regulatory Commission, a process that could take nearly a year. But under the new law regulating the post office that took effect in late 2006, the agency can increase rates with 45 days' notice as long as changes are within the rate of inflation for the previous 12 months.
The Postal Regulatory Commission calculated that rate at 2.9 percent through January, limiting the first-class rate to an increase of just over a penny.
Also going up
Other increases set for May 12:
-Post cards up a penny, to 27 cents.
-Certified mail, $2.70, up 5 cents.
-First-class international letter to Canada or Mexico, 72 cents, up 3 cents.