(1) An offer may be served—(a) for a jury trial of a proceeding started by claim—at any time before a verdict is returned; and(b) otherwise—at any time before final relief is granted.
(2) However, if an account is claimed in the first instance or if a claim involves taking an account, an offer may be served at any time before the certificate under rule 540 becomes final and binding.
(3) Further, if there is a judgment conditional on the assessment of damages, an offer may be served at any time before the damages are assessed.