Consumer has a 5 year ARM (30 years in total). They have paid as agreed for 15 years. Their rate is high in today's market and they want to know if they can modify the loan from a variable interest rate to a fixed interest rate. Would this be considered a modification or a refinance?

The term "modification" is not used in Regulation Z and therefore is irrelevant in determining whether the proposed post-consummation event will trigger new disclosures. To be relevant, an event must rise to the level of a "refinancing" (as defined by Section 1026.20(a).)

"A refinancing occurs when an existing obligation that was subject to Subpart C is satisfied and replaced by a new obligation undertaken by the same consumer." Will your proposed modification result in satisfaction and replacement of the original note with a new note?

"Even if it is not accomplished by the cancellation of the old obligation and substitution of a new one, a new transaction subject to new disclosures results if the creditor...adds a variable-rate feature to the obligation." Since you are removing, not adding, a variable rate feature, this additional test (found in an Official Interpretation of Section 10236.20(a)) does not apply in your case.