“I’ll believe it when I see it” for things that aren’t supposed to be referred to visually? [closed]

Solution 1:

I think the idiom I'll believe it when I see it should work in the example you have given. It may refer to the money owned or the whole thing - paying back. Remember that the idiom is used for expressing doubt that something will happen or be. In other words:

I'll pay you back, I promise! - I highly doubt it will happen = I'll believe it when I see it.

Alternatively, you might say:

I'll pay you back! - Don't feed me empty promises! / Actions speak louder than words! / It's just talk (and no action)!

Solution 2:

The idiom "I will believe it when I see it" seems to be very apt to the context as you explained. See the M-W Dictionary gives another idiom together with the one you have put in question and an example sentence to be used in a context like that of yours!

wasn't born yesterday (idiom)

Definition of wasn't born yesterday —used to say that someone is unlikely to believe something that is not true or to trust someone who is not trustworthy

He said he'd pay me back, but I'll believe it when I see it. I wasn't born yesterday.