From Longman Business Dictionary
retroactiveret·ro·ac·tive /ˌretrəʊˈæktɪv◂-troʊ-/ adjectiveadj formalLAW a law or decision that is retroactive is effective from a particular date in the pastSYN RETROSPECTIVEretroactive toThe company said it will adopt the new accounting method retroactive to Jan. 1.
—retroactively adverbadvThe pension benefitsapply retroactively to employees who retired on or after last Dec. 31.