Songfacts®:

• This unrepentant pop celebration finds Anne-Marie indulging herself on her special day.
  
  It's my birthday
  I'ma do what I like
  I'ma eat what I like
  I'ma kiss who I like
  It's my birthday
  
  Because it's her birthday, Anne-Marie will not hold back. She explained to Genius there will be no containing of her celebrations: "When it's people's birthdays, I just feel like they deserve everything. When it's my friends' birthdays, it's my favorite day because all day long I want to throw them a party and I want to make them feel special and I want them to have presents and just that they're excused for everything they want to do. They can do whatever they want."
• Anne-Marie sings in the pre-chorus about trying to distract herself from thinking about her ex by getting off with someone else. She explained that writing the chorus came easy to her, as she could just talk about doing what she wants to on her birthday. However, the rest of the song was trickier because she'd said everything she wanted to say in the chorus and she felt it needed more grit. Her solution was to bring her ex-boyfriend into the song. "He kind of made the subject a little easier to arrive at," she said. "He always does."
• Anne-Marie wrote the song with Delacey (Halsey's "Without Me," Zara Larsson's "Ruin My Life") and Warren "Oak" Felder of the production duo Pop & Oak. They penned the tune in October 2019 when, with the festive season around the corner, Anne-Marie was wondering why there were more Christmas than birthday songs.
• After Anne-Marie told Felder she wanted to write a birthday song, the producer was initially unsure. But once he'd laid down some chords and Anne-Marie started singing the chorus, they all came round to the idea and quickly completed the tune.