154. Form and content of a Part 18 offer

(1) A Part 18 offer must be in accordance with the prescribed form.
(2) The offer must make clear that it is made pursuant to Part 18, must specify a period of not less than 21 days within which the defendant will be liable for the claimant's costs in accordance with paragraphs (1) to (4) of Rule 161 if the offer is to be accepted; state whether it relates to the whole of the claim or to part of it or to an issue that arises in it and if so to which part or issue; and state whether it takes into account any counterclaim.
(3) Paragraph (2) of this Rule does not apply if the offer is made less than 21 days before the start of a trial.
(4) A Part 18 offer which offers to pay or to accept a sum of money will be treated as inclusive of all interest until the date on which the period specified under paragraph (2) expires or, if paragraph (3) applies, a date 21 days after the date the offer was made.