The official Twitter accounts for the Queen and the Duke and Duchess of Cambridge have posted birthday greetings.

An image of the Queen and her grandson, during a 2017 Buckingham Palace reception, was featured on the royal family account, along with the words "Wishing The Duke of Sussex a very happy birthday!" and emojis of a cake and balloon.

While William and Kate's account said: "Wishing a very happy birthday to Prince Harry today!" and was accompanied by a picture of the Cambridges and Harry racing each other at a 2017 event supporting their Heads Together mental health campaign.

The duke's birthday follows an eventful year that has transformed his life.

Harry is now living in California with wife Meghan and son Archie after they made the sunshine state their home just before the coronavirus lockdown began in March.

The couple are likely to celebrate the duke's September 15 birthday privately at their Santa Barbara home as the prevalent COVID-19 cases have forced restrictions on the city's bars and restaurants.

Harry and Meghan's new life in America is progressing fast, with the couple signing a deal with Netflix to create films and programs - estimated to be worth more than $US250 million.

The couple stepped down as working royals in March for financial and personal freedom and the contract has enabled them to pay back the STG2.4 million of taxpayers' money used to renovate Frogmore Cottage, their UK home in the grounds of Windsor Castle.

A source has said they are no longer receiving financial support from the Prince of Wales and viewed the payment as "another significant step in their new life".

Australian Associated Press