I'll take a rain check

I'll take a rain check (American, British & Australian, informal, American, informal)

something that you say when you cannot accept someone's invitation to do something but you would like to do it another time. I'll take a rain check on that drink tonight, if that's all right. (often + on) I won't play tennis this afternoon but can I get a rain check?

See also: check, I'll, rain, take