Islanders are to be charged an extra 5p for posting items to the UK and an extra 4p locally. The decision follows the introduction of charges by the Royal Mail on Guernsey's post.
The regulatory manager at the Office of Utility Regulation (OUR), Jon Buckland, says prices have to go up to ensure the postal service in the island continues.
A local stamp will rise by 7% to 26p and stamps for post being sent to the UK will cost 32p.
Mr Buckland says the increases are due to the introduction of charges by the Royal Mail for delivery of Guernsey mail to the UK and worldwide.
Once it comes into effect, the prices will then be capped for the next two years.