Chris Jackson - Pool/Getty Images Princess Charlotte
"Thank you for the kind birthday message which you sent for Princess Charlotte's seventh birthday," the note said. "Princess Charlotte had a lovely day and your message was greatly appreciated by the Duke and Duchess of Cambridge who send you their very best wishes."
Featured on the card was one of Princess Charlotte's three birthday portraits, which were taken by Kate.
The photos showed Princess Charlotte posing in a field of bluebells near the family's country home, Anmer Hall.
In one sweet snap, she hugs the family's new dog, Orla. William and Kate, both 40, adopted a cocker spaniel into their family from a litter raised by Kate's brother, James Middleton, in late 2020 after the death of their beloved pup Lupo.
Princess Charlotte has already had a big year. In addition to joining the royal family at the Platinum Jubilee celebrations in June — where she helped her parents keep an eye on 4-year-old brother Prince Louis! — she had her first solo outing with her parents last month when she joined them at the Commonwealth Games.
Joe Giddens/PA Images via Getty Kate Middleton, Princess Charlotte and Prince William
Princess Charlotte is also gearing up for a new school year — at a brand new school. The family is relocating from Kensington Palace in London to their new home in Windsor.
"The move is mostly down to schooling," a family friend tells PEOPLE.
Their new home will be a 10-minute walk from Queen Elizabeth, 96, and a short drive from Kate's parents, Michael and Carole Middleton, in Bucklebury, Berkshire.
Windsor, with its vast parklands, will enable the children to have friends over for playdates and to be able to walk their dog or have company over in complete privacy.