According to the OSFI guidelines, all federally regulated financial institutions must verify the source of the down payment before putting the seal of approval on a mortgage. They must check this to ensure the funds come from a legitimate source, not something illegal. But even if your mortgage lender isn’t federally regulated, you must be ready to prove your down payment source. That’s because non-federally regulated financial institutions also follow these verification processes to prevent fraud and comply with anti-money laundering regulations.