My name is on the mortgage(my name only) but not on the deed. So the deed is in one name and the mortgage in another. If I should quit paying the mortgage, what would happen to the house?

You have to give some more details.

Is your name on the mortgage or the mortgage note (or both)? The mortgage note is the paper that states that you owe the money. The mortgage is the paper that says you will lose your property if you don't pay the money.

Were you ever named on the deed in the past?

Whose name is on the deed?

Whose name is on the mortgage?

Whose name is on the mortgage note?

What are the relationships?

If you are truly the only person named on the mortgage, and you are not an owner of the house, then this is not really a mortgage. Instead it's a personal loan. A true mortgage uses the house as collateral for the loan, so that if you don't pay the bank can repossess the property. But if you are not an owner of the property you have no right to put the house up as collateral. (By the way, since you have nothing at risk here you are precluded from deducting any mortgage interest payments from your income taxes.) So if you stop paying the mortgage the bank would certainly sue you for nonpayment, and your credit score would be ruined, but it seems that the loan is uncollateralized (like a credit card) so they can't do anything about the house itself.

How exactly did this come about?

But if your name was on the deed and signed a new deed over to someone, without paying the loan off or without notifying the lender of the new deed, The courts may find that the new deed is not valid and/or that the lien still exists on the property since it was not paid off at the sale.

So it could be a very serious legal issue depending on how things got this way

My moms house was mortgaged in her name. She deeded it to my sister. My mom passed away. The bank does not want to honor the deed. What should we do?

Your sister has to refinance the mortgage immediately to prevent the current lender from foreclosing. If the current lender will not modify the loan to your sister's name then your sister will have to find a loan somewhere else. Another option is for your sister to sell the house and have the loan paid off at the closing.

The transfer to your sister is still valid but since the lender was never paid off and did not modify the loan, the lender has the right to foreclose on the property.

It will go delinquent and everntually fall into foreclosure, however the deed is not what dictates whose credit score is affected, it is the NOTE!