/ˌrɛtroʊˈæktɪv ɪˈfɛkt/ – Phrase
Definition: có hiệu lực trở về trước, có hiệu lực hồi tố.
A more thorough explanation: The legal English definition of the term “retroactive effect” or “retrospective effect” refers to a law, regulation, or decision that applies to past events or actions, altering the legal consequences of those events or actions as if the new law had been in place at the time they occurred. This means that the law has a backward-looking impact, affecting situations that occurred before the law was enacted or came into effect.
Example: The new tax law will have a retroactive effect, meaning that it will apply to income earned in the previous year.