Must a mortgage company have original documents in order to prove debt? If bank can not produce original documents of mortgage. Is debt still valid

Why do you ask?

Yes, and no. And it depends on what state or country it's in.

Here in Florida, for example, they can foreclose, but cannot go after a deficiency judgment.

I am upside down in mortgage. Mortgage has been sold many times in last few years> I have repeatedly tried to to get loan modifications . When talking to most recent collection agency they have no record of my wife being on the loan. We were joint signers. I do not believe that they have the real documents anymore. I asked present collection company for proof of debt and copies of original papers and they have stopped talking to me.

Yes, and no. And it depends on what state or country it's in.

Here in Florida, for example, they can foreclose, but cannot go after a deficiency judgment.
I am In Mass

There is usually sufficient corrobative proof that you have been paying the loan to at least confirm the debt.

I am upside down in mortgage. Mortgage has been sold many times in last few years> I have repeatedly tried to to get loan modifications . When talking to most recent collection agency they have no record of my wife being on the loan. We were joint signers. i do not believe that they have the real documents anymore. I asked present collection company for proof of debt and copies of original papers and they have stopped talking to me.

If it's a mortgage, and the note has been sold, they will have copies of the note and mortgage. And if they sue you to foreclose, they will probably have to attach the copies to the complaint they file in court. You will get copies at that time.

It has been fought a few times in court. There are a few cases where the foreclosure was halted, but most still go though,

You may hire an attorney and fight it, if you want,