For the record, a one-bedroom apartment in the Cupertino area rents for $2,500+ a month on average; an apartment for 4 in the Cupertino area would rent in the 4,000-5,000+ range, which indicates the “culprit’s” family is probably piled into a small two-bedroom apartment.
I understand why OP won’t provide us with the information s/he has, but what was mentioned is absolutely not compelling, and unless the “culprit” falsified tax forms (which is very difficult to do), QB is very thorough in what documents it asks for (it’s not like COmmonApp where you just “declare”) so it’s hard to imagine someone CAN have committed a fraud, unless they also defraud the IRS and their employer is in on the scheme.