I own a home jointly with a partner. I have made all the payments, taxes and insurance since the beginning. I have a buyer for the home but my partner does not want to sell. How can I override his decision?
My answer assumes the sale is necessitated by divorce.
If your partner does not want to sell, perhaps they want to buy?
Let's set aside for a moment the fact that you made all the payments on the property; that money is gone. Your partner will argue that while you took care of all the payments they took care of other stuff that was equally beneficial to the marriage and cancels that out. A judge would support that argument. In future, consider a pre-nupital agreement.
If you have a buyer willing to purchase at a specific price you have a good starting point for negotiations with your partner; a sale price.
Now add up all the expenses involved with selling a house: lawyer fees, land transfer tax, realtor fees, early mortgage cancellation fees, and the amount owing on the property. Subtract these fees from the purchase price, divide by 2, and offer to take your name off the deed and the mortgage for that price. If your partner is reasonable they get to stay in the house, you get some cash in your pocket and walk away from the deal with minimal hassle.
This type of deal is known as a "shotgun deal", where either party can offer the other the same thing. By that I mean your partner could offer you the same amount of cash to sign off on the property. From your question, it seems unlikely this will happen. A deal that is equitable and fair can save a lot of headache for both parties.