The Royal Mail is increasing the cost of postage, with first-class stamps rising 6p to 76p and second-class up 4p to 65p.
Prices will climb from 23 March, less than a year after they were hiked to their current levels.
The 65p second-class stamp is the maximum under an Ofcom price cap.
"These changes are necessary to help ensure the sustainability of the one-price-goes-anywhere Universal Service," Royal Mail said.
It blamed the increases on "a challenging business environment".
