Hal_Al
Level 15

Deductions & credits

Do a little research, make your best guess and hope you don't get audited.  For example this graph indicates houses were worth about 25-30% of today's value, back in 1986. 

https://dqydj.com/historical-home-prices/

 

If you owned it in 1986, do you have some record of RE tax paid (check register, deduction on tax form)?  Compare that to current tax bill.