Do I owe taxes on money received from the sale of my living stepmom's house that I never lived in and for which I received a substitute 1099-S?

[borsa2]

I was not aware of the sell until I was notified to come to the closing to get my 25% share of the proceeds along with my stepsister. That is when I learned that my name was on a Warranty Deed with Vendor's Lien "as inherited property."  Also, 25% of the closing costs were deducted from the proceeds that I received. It is my understanding that my father did not leave a will when he died in 1999.

[Phillip1 · Accepted solution]

Yes, there will be some tax due from the sale of this property. 

The amount of tax depends on whether you inherited the property when your father died in 1999, or whether the home was given to you by your stepmother. 

If the home was inherited when your father died in 1999, your basis will be 25% of the 1999 fair market value of the home. 

If the home was given to you by your stepmother, there are two possible results. In this case the home was inherited by your stepmother and your basis will be 25% of her basis. If she lives in a community property state, her basis will be the fair market value on the date of your fathers death in 1999. If she doesn't live in a community property state, the basis will be half of the fair market value of the home when your step father died and then half of the purchase price of the home (if they purchased the home while they were married).