Formal transfer of an existing mortgage to a buyer who takes over the debt obligation under the lender's approval process.
An assumption of mortgage is the formal process in which a buyer takes over an existing mortgage and becomes responsible for the debt under the terms approved by the lender.
Mortgage assumption matters because it can preserve favorable financing for the buyer while changing who is responsible for repayment. It also changes the liability picture for the seller, who may or may not be fully released depending on the lender’s approval terms.
Assumption is a transaction process, not just a loan attribute. The starting point is usually an Assumable Mortgage, followed by lender review of the incoming borrower.
| Structure | Buyer liability | Seller liability after closing | Lender role |
| — | — | — | — |
| Assumption of mortgage | Buyer formally takes responsibility | May continue unless lender releases seller | Usually active approval and qualification |
| Subject-to mortgage | Buyer often avoids formal personal liability on the note | Seller often remains directly exposed | Formal approval may be absent or limited |
| New mortgage origination | Buyer takes new debt only | Seller’s old mortgage gets repaid | Lender underwrites a new loan |
The practical issue is not only whether the buyer wants the existing terms. It is also whether the lender approves the transfer and whether the seller receives a true release from continuing liability.
A buyer wants to purchase a property with an existing low-rate FHA loan. Instead of replacing the loan with a new higher-rate mortgage, the buyer applies to assume the existing debt. If approved, the buyer takes over the loan payments and the old mortgage stays in place rather than being paid off at sale.
In a Subject to Mortgage deal, the buyer takes title subject to the existing debt without necessarily becoming the formally approved borrower on the note.
Even when the buyer assumes the mortgage, the seller may still need explicit lender release to be fully removed from continuing liability.
Assumable Mortgage: The loan feature that makes a formal transfer possible.
Subject to Mortgage: A similar-looking transfer structure with a different liability result.
Due-on-Sale Clause: A key transfer-risk provision in mortgage contracts.
Mortgage: The broader financing contract being transferred.
Refinancing: The common alternative where the old loan is paid off and replaced.