Rule 3221. Offer to compromise. Except in a matrimonial action, at any
time not later than ten days before trial, any party against whom a
claim is asserted, and against whom a separate judgment may be taken,
may serve upon the claimant a written offer to allow judgment to be
taken against him for a sum or property or to the effect therein
specified, with costs then accrued. If within ten days thereafter the
claimant serves a written notice that he accepts the offer, either party
may file the summons, complaint and offer, with proof of acceptance, and
thereupon the clerk shall enter judgment accordingly. If the offer is
not accepted and the claimant fails to obtain a more favorable judgment,
he shall not recover costs from the time of the offer, but shall pay
costs from that time. An offer of judgment shall not be made known to
the jury.