@ahowardnc
If you are listed as a property owner, you are responsible for any capital gains tax. Capital gains is the difference between the selling price and the adjusted cost basis. The cost basis is what your mother originally paid to buy the home plus certain adjustments. Adjustments to cost basis can include permanent improvements made to the home or reductions for business use of the home. If your mother previously owned the house with your father and he has passed away, that also creates an adjustment to the cost basis, but exactly what kind of adjustment depends on whether your parents lived in a community property state or not.
So the first thing you need to do is determine the adjusted cost basis. This can be complicated and we may be able to provide more advice depending on the situation. You can also read IRS publication 523. https://www.irs.gov/pub/irs-pdf/p523.pdf
Then if you owned 1/3 the home, you would report 1/3 of the selling price, and 1/3 of the cost basis, and you would pay capital gains tax on the difference. Your mother would report 2/3 of the selling price, and 2/3 of the cost basis, but the first $250,000 of the gain would be tax free to her because it was her main home.
If you did not actually receive the cash, and you were only on the title “in name only“ for estate planning purposes, you still owe the tax on your share of the capital gains. The transaction should have been handled differently from the beginning, but it is too late for that now.
If you want to find a way to not pay tax on your share of the home, you will need to talk to a local professional tax accountant. Alternatively, you could pay the tax and your mother could reimburse you for the tax.
