Will sell a second house in 2021. It has no mortgage, has been empty for several years. We bought it in 1980 for 36,000. Tax ramifications?

[neptune2]

Gain likely 75,000-100,000 over purchase price

[tagteam]

If you have ever used the house as rental property, you will almost certainly have a depreciation recapture event with which to deal.

If the house has always been used as a second home (never "business property"), then the calculation is simple:

Selling Price LESS selling expenses LESS adjusted basis EQUALS gain (or loss). In your case, this would be long-term capital gain (taxed at more favorable rates than ordinary income).

See https://www.irs.gov/publications/p523#en_US_2020_publink100010751

You need to ensure that you factor in your basis adjustments, such as improvements made over the years, closing costs, and any casualty losses.

[Critter-3]

Purchase price + costs to BUY + costs to SELL = cost basis

Selling price - cost basis =  long term cap gains  taxed at no more than 20% ( + a possible 3% NIT tax).