Deductions & credits

Hi, I've seen this term used often - "cancelled check". What exactly does that mean?

 

Let's say I give $60 to a church - and it's $60 in cash (as in green money, twenty dollar bills, cash). What am I supposed to do to substantiate that? Fill out a check, and just write "CANCELLED" across it, and then keep it for my records?

 

Or does it mean something else?

 

Thanks