Como dizer "é por minha conta" em inglês

You may say:

• It's on me!
• My treat!
• It's my treat!

On the house. (Por conta da casa.)

There is also the expression "on someone_here dime"

For example: "Hey, do you want an extra drink? It's on our dime!"
"Hey, quer outra bebida? É por nossa conta!"

I hope that helps

Just complementing my previous post, here goes a video where you can hear "on our dime" (00:50):

Warning : There is a HUGE spoiler of the 4th episode of Lost (from the 1st season).
Transcript: "I'll get you on a plane back to Sydney on our dime. It's the best I can do."

Hope it helps

A general comment, (not just for leisure activities) is "I will foot the bill".

Seria certo dizer:

"Would you like to join me for a business meeting today? Don't worry, the capuccino is on my dime."?

Ranato,

Sim, a expressão "on sb's dime" quer dizer "por conta de alguém", "pago por alguém".

A. Who’s paying for the kids’ trip then?
B. They’re traveling on my dime!-->Vão viajar por minha conta.

Don´t worry, the capuccino is on my dime.
Não se preocupe, o capuccino é por minha conta.

Bons estudos!

Bom, uma pergunta lógica mas mesmo assim vou perguntar, há alterações nos pronomes possessivos?

Exemplo:

It's on me/you/him/her/them/us!
My/his/her/our/their/your treat!
It's my/his/her/our/their/your treat!

I'm gonna eat too much pizza already they are his treat. [ Eu vou comer muita pizza já que elas vão ser por conta dele. ]

In the UK, we use 'It's my shout' especially when it is regarding drinks at a bar!