I'll keep this very short because it's not all that complex.

A couple of years ago a friend didn't pay me back for a food order, I had asked for it a couple of times, but then I didn't see them for a couple of months and I felt it was perhaps too late (the sum wasn't ridiculous). Anyway, recently I owe them a similar amount for food, they haven't brought it up, but I am obviously aware I didn't pay for mine. 
AITA for not paying them back, consciously. Because I know them pretty well and I think they honestly forgot to pay me back initially.

Sorry it's not as interesting as most the posts, just curious for everyone's opinion.