We are full pay. Did not fill it out with D#1 - she got plenty of merit. With D#2 (2021 hs grad), I learned for the first time on here that some schools may REQUIRE the FAFSA in order to receive merit aid. One of the schools in D#2’s top 3 had this requirement, so I filled it out. I did the best I could with recent tax return information (and they have all your info, so they can check it - plus you agree to link it to your IRS filings at some point), so there were probably some mistakes but no one contacted me either way - to answer the OP’s initial question.
Again, via research on here, the consensus was that it didn’t hurt to submit it to all the schools she applied to - so I did. A couple of the schools contacted me regarding the additional requirement of the CSS. I was not going to take the time needed to fill out the CSS (plus, I was uncomfortable with the level of info it asks for). Of the two schools that asked for it, one was an in-state reach (so, affordable for us and limited merit only given for the very top of the class) and the other was a private that was very low on her list. I contacted both schools and confirmed that it was fine not to do the CSS as long as I understood that she’d be out of merit contention. She did end up getting a merit award from the school that required the FAFSA only as well as good merit from the non-FAFSA schools.
I would research whether the schools your student is applying to have the FAFSA/CSS requirement for merit awards. If they don’t, and you are comfortable with your financial position, I wouldn’t bother filling them out - but that’s just me.
Agree with this - don’t think you need to do it just for work study. At D21’s university jobs in the dining hall are not work study and they are starting at $15/hr with free meal vouchers.