Ofcom today fined Royal Mail £1.5 million for failing to meet its regulatory first-class delivery target in 2018.
Royal Mail is required by Ofcom to deliver at least 93% of first-class post within one working day. But last year 91.5% of first-class post was delivered on time.
Ofcom said Royal Mail failed to provide any reason why it missed the target.
Ofcom said: "It did not provide a satisfactory explanation and it did not take sufficient steps to get back on track during the year. So we have decided to impose a fine of £1,500,000 on Royal Mail for failing to meet its first-class delivery target."
The regulator has also fined Royal Mail £100,000 for overcharging customers for second-class stamps between 25 March and 31 March last year.
Ofcom added: "For 1 April 2018 to 31 March 2019 the cap was set at 60p. Royal Mail increased its price for second-class stamps to 61p on 25 March 2019, thereby overcharging customers for seven days until the cap increased on 1 April 2019.
"The company estimated that it overcharged people by approximately £60,000 in total as a result, which it is unable to refund."
Gaucho Rasmussen, Ofcom's Director of Investigations and Enforcement, said: "Many people depend on postal services, and our rules are there to ensure they get a good service, at an affordable price.
"Royal Mail let its customers down, and these fines should serve as a reminder that we'll take action when companies fall short."