What is this Invoice?

C: I looked you up in the phone book and couldn’t find you. This must be a scam
Me: no sir it’s a paid invoice from when Tech2 came out to install your printer, the invoice is for your taxes
C: I already did my taxes
Me: sir services were for this year you couldn’t have claimed it but that is neither here nor there.
C: Oh I’m sorry. I thought this was a scam.
Me: no problem sir, have a great day.