How thoroughly do colleges and financial aid institutions verify the
custodial parent section of the FAFSA? The Expected Family
Contribution (EFC) is based on the data provided by the custodial
parent.

My ex-wife and I both ran the numbers for the EFC, and if I am
considered the custodial parent, our EFC is $23,000, but if she is
considered the custodial parent, our EFC is $5,000.  Big difference.
Our daughter lived with me most of the past year, and I am the legal
custodial parent, but I am not a wealthy person by any means, and
contributing  23K per year is not remotely possible.

 I would like to let my ex-wife claim my
daughter on her tax forms next year if we could use her financial
income for the FAFSA.

Putting aside questions of ethics, fairness, legality and the like, if
we used the lower income on the FAFSA, do they cross-check that with
where the child attended school or require some sort of proof of
residence, or will it simply be enough that the "custodial parent"
listed on the FAFSA matches the parent who claimed the child as a
dependent for that year?