A proper 998 settlement offer must include a provision that allows the opposing party to accept the offer by signing a statement that the offer is accepted.  A purported 998 offer lacking that provision cannot be used to shift costs if it is not accepted.  (Puerta v. Torres (2011) 195 Cal.App.4th 1267.)  This decision holds that the deficient offer also is ineffective if accepted.  No valid judgment may be entered based on acceptance of a purported 998 offer lacking the required provision allowing acceptance by signature.