If you owned and lived in the property for two out of five years as of the date of the sale, then you will qualify to exclude up to $250,000 ($500,000 if filing
MFJ) of capital gain from taxation
. I assume you have not rented any portion of the property nor have you taken an exclusion within the last two years on another residence sale.
If you meet these criteria then you can sell to your partner and exclude some or all the gain. If you do not meet the two year ownership and residence test as of the date of sale, and you do not qualify for an exception, then you will be taxed on the gain.
You could gift the property to your partner but there would be complications if you owe a mortgage on the property. If you gift your interest
in the property, to the extent you owe debt you will be treated as selling the property, subject to the same exclusion rules
I cited above. You may also be required to file gift tax returns
and use some of your lifetime exclusion (currently, $1,500,000).