The situation you described is common -- one married person may appear on a mortgage or property title for myriad reasons. The name of what you called a form varies by state. In most states it is not even a form. The letter to the county clerk is often just called "recording instructions" or something equally non-descriptive. It is prepared by the title company or escrow company.
Consult with your real estate agent, title company, or attorney who is handling the transaction for the exact name of this document in your state.
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