e.g. if you made a big buy there ought to be records of a bank transfer, mortgage, etc.

"i paid for 30 acres here at $xx rate, and here is the mortgage docs from the bank dated March 19th that I signed, plus their valuation of the property and what went into it"

Lots of land deals aren't dealt in money transfer either. It's sometimes cash, livestock transfer, other realstate or durable goods like cars or machinery.