Royal Mail must deliver letters to every address in the UK six days a week, and at a standard price according to its universal service obligation.
The chief commercial officer at Royal Mail Nick Landon said: “Like other companies, 2020 has been a challenging year for Royal Mail.
“Our people have worked tirelessly to keep the UK connected throughout the pandemic and associated restrictions.
“These price increases will help us continue to deliver and sustain the universal service in challenging circumstances.”