Legal Question in Real Estate Law in California

This cannot be answered in the abstract. It depends on what you are doing in the modification and whether it is covered by the existing deed of trust. If it is not covered you may have to do a new DoT and may have to get subordinations as well. One BIG word of warning, though, do not record a modification of anything if there is a second, or any other debt or liens against the property that have recorded since your first trust deed, without advice and assistance of a knowledgeable land title and real estate attorney. If you do, those liens may very likely jump ahead of yours.

It is customary to record a deed of trust, but not the promissory note that the deed of trust secures. Indeed, a promissory note probably cannot be recorded. If the modification makes no change to anything in the recorded deed of trust, I'd see no reason to record a new deed of trust. Note that institutional lenders will have well-established practices and will insist they be followed. I assume your lender is a friend or relative or at least a very small lender. Maybe you should get local attorney advice on the whole transaction.

Keep in mind that re-recording a loan may affect its priority, if other liens have been recorded in the interim. For this reason, lenders generally prefer not to re-record, other things being equal.

A modification can restate all the terms or only those modified, but in either case the new promissory note should be complete either in itself, or by making reference to the prior note and incorporating the unmodified terms into the new note. It should be clear that the new note is a replacement for the old one (if this is the parties' intention) and not an additional obligation of the borrower. (Actually, there are three possibilities: (1) new note is an additional obligation; (2) new note is an alternative obligation that the borrower may pay under so long as he doesn't default, in which case the lender can sue under the old note; and (3) the new note extinguishes and replaces the old note -- is a "novation" -- and the lender's rights are limited to the new note).

I should probably also point out that loan modification services are now regulated by law, Civil Code sections 2944.6 and 2944.7, and that the Feds have a couple of loan-modification programs going under the acronyms "HARP" and "HAMP."