Is it permissible for a qualified plan loan to be refinanced, say at a lower interest rate?

Probably start w/ review of the Plan's loan provisions and loan policy. May be limits on number/frequency of loans as well as Plan/ERISA loan amount limits. Generally, there should not be an absolute prohibition. Participant can always payoff existing loan and proceed w/ de novo loan of equal amount. BUT, I believe you also have to be sure the new loan is not a prohibited extension of the payback term of the original loan. Not sure if there would be unique treatment if original loan was for purchase of prinicpal residence w/ extended payback.