The Postal Service is adding a larger flat-rate Priority Mail box and a charge for Sunday and holiday delivery, the first changes it has made under a law approved last year governing mail operations.
Previously such changes would have to be announced and go through a lengthy hearing process before going into effect.
The new law smoothed the process. The post office said Thursday the changes will take effect March 3.
A new flat-rate Priority Mail box will become available at $12.95 for shipping anywhere in the United States. The agency will discount it to $10.95 for shipping to military addresses.
The new box measures 12-inches-by-12-inches-by-5.5-inches, containing nearly 800 cubic inches of space. Two smaller flat rate boxes will still be available for $8.95. They are each a more than 500 cubic inches.
In addition, the agency said it will begin charging a $12.50 premium for delivery of Express Mail on Sunday or holidays. Previously the Postal Service has not changed extra for delivering on those days.