Help wanted TRS for FTB complicated...

Help wanted: My partner and Myself purchased a house in May 2000, a contract was raised due to the fact at the time I was separated (I’m now divorced) basically it was as if we were two unconnected individuals purchasing the house. The Mortgage company did not submit to the tax office that my partner was a first time buyer; so therefore we have only been receiving a TRS based on no ftb upper limit for my partners piece of the mortgage.
This only came to light this year; yes we were extremely negligent in not picking it up for all this time!!
We contacted our mortgage broker who apologised for the omission and advised us to reapply to the tax office for the backdated TRS…we filled in the form with all relevant interest certs etc…My question is what is realistic to expect on backdated monies (if any) at this late stage?

If you are genuinely owed back relief then you will get it - but only for the previous 4 tax years and not all the way back to 2000 since there is a 4 year limit on backdated tax reclaims.