Lenders differ in their mortgage modification requirements, but typically they require you to show that: You're at least one regular mortgage payment behind, or a missed payment is imminent. You've incurred significant financial hardship, for reasons including: Long-term illness or disability.
Strictly speaking, a modification to a mortgage does not need to be recorded to be enforceable between the borrower and the lender, as they are bound by the modification as a matter of contract law.
Generally, once you've locked in a mortgage rate, the terms are fixed and usually cannot be renegotiated. However, some lenders offer a float down option, allowing you to negotiate mortgage rates if market conditions shift favorably during the rate lock-in period.