retroactively
adv. C1 Advanced US //ˌɹɛtɹoʊˈæktɪvɫi// UK //ɹˌɛtɹəʊˈæktɪvli// retroac·tive·ly
adv. to apply a rule or change to a situation that already happened in the past. You use this when a new law or decision affects things that happened before it was made.
adv. to apply a law, rule, or decision to events or situations that occurred in the past. Often implies a change in status or legal standing that is effective from a date prior to the current one.
The new tax law applies retroactively to last year's income.
The court ruled that the contract was invalid from the start, applying the decision retroactively to the original signing date.
While the amendment was passed in the current fiscal year, its retroactive application means that all previous filings must be adjusted to reflect the new standards.