I have also had my mom sign the FSA form once for some babysitting she did. It was never questioned. However I think that personally, if I were going to do this on a regular basis, I'd be more comfortable with everything being reported, I think that would mean you'd have to give the sitter a 1099 and report the income? Very good chance it would never be investigated buuuuuuut you never know and I'm definitely too much of a rule follower. I have mostly used the FSA for preschool so don't know for sure. Sorry I can't be more help.