These words are often treated as interchangeable. They are not. A notice that says a clause operates “retroactively” when the drafter meant “retrospectively,” or a submission that a policy is “proactive” when the point was that it looks only forward, breeds the ambiguity that litigation feeds on. The words are cousins; the consequences they carry are not.
Prospective is the baseline. A prospective law governs acts, events and transactions that occur after it comes into force. It leaves the past alone. This is not a convention of drafting but a presumption of construction: unless the legislature says otherwise, a statute is read as speaking to the future. A Constitution Bench restated this in Commissioner of Income Tax v. Vatika Township (P) Ltd., (2015) 1 SCC 1, invoking the maxim lex prospicit non respicit — the law looks forward, not back. The reason is fairness: a person is entitled to arrange his affairs by the law as it stands, and should not find those arrangements upset by a later rule. Where a statute is silent, prospective operation is the default the court supplies.
Retrospective is the departure from that baseline. A retrospective provision reaches back to attach new legal consequences to transactions already completed — it may take away or impair a vested right, impose a new obligation, or fasten a new disability on something done before the law existed. Because it disturbs settled expectations, the presumption runs against it: retrospective effect must be expressed in clear words or arise by necessary implication. The drafting signals are familiar — “shall be deemed always to have been,” “with effect from [a past date].” One exception softens the presumption: an amendment that is curative or declaratory — one that explains what the law always meant rather than changing it — is read as retrospective, because it creates no new burden. In Vatika the Court read the legislature as drafting with three effects in view: a prospective amendment operating from a fixed future date, a retrospective amendment operating from a fixed anterior date, and a clarificatory amendment retrospective by its nature. The words on the page decide which of the three a provision is.
Retroactive carries that departure further. Retrospective operation changes the future consequences of a past act; retroactive operation rewrites the past act itself, treating the new law as though it had always been in force. A provision deemed “always to have meant” something, or a validation Act that cures a levy a court has struck down and declares past collections good, works this way — it reaches back and alters the legal facts as they stood, not merely their future effect.
The courts hold this line less firmly than commentators do. In Vatika the Bench spoke throughout of “retrospectivity”; in Golaknath, defining prospective overruling, the Court spoke of refusing to give its ruling “retroactivity” — the same backward reach, a different word. The label earns its keep when the effect of a provision is in dispute, where what matters is whether it alters past facts or only their future consequences.
Ex post facto is the criminal-law face of the same problem, and here the Constitution turns a presumption into a prohibition. Article 20(1) forbids conviction for an act that was not an offence when it was committed, and any penalty greater than the one the law allowed when the act was done. The bar is that specific: it strikes at retrospective criminality and enhanced punishment, not at procedural change, which may apply to past acts; and it does not stand in the way of a later reduction in sentence that operates in the accused’s favour.
Prospective overruling belongs to a different vocabulary — that of judicial technique, not statutory operation. When a court overrules an earlier interpretation but confines the new position to future cases, leaving past transactions decided under the old view undisturbed, it overrules prospectively. The device entered Indian law through I.C. Golaknath v. State of Punjab, AIR 1967 SC 1643, where Subba Rao CJ described it as a pragmatic tool that preserves the past while protecting the future. As first laid down it was fenced: to be invoked only in constitutional matters, only by the Supreme Court, with the reach of the new position left to the Court’s discretion. Later Benches have relaxed the first two limits, applying the technique beyond constitutional questions. It is easy to conflate “prospective overruling” with “prospective legislation”; they share an adjective and nothing else.
Proactive does not belong here at all. It strays into legal writing because it sounds like a temporal antonym of retrospective, and is not one. It carries no meaning about when a rule operates; it describes an attitude — acting in anticipation rather than in reaction. Its home is administrative and policy language, as in the “proactive disclosure” obligation under Section 4 of the Right to Information Act, 2005, where a public authority must publish information on its own motion rather than wait for an application. Reach for “proactive” to describe when a statute operates and you have said nothing about time; the word you wanted was prospective.
The discipline is worth keeping. When operation in time is the point, choose between prospective and retrospective, and keep retroactive for the stronger sense of rewriting the past. Keep ex post facto for penal consequences and Article 20(1). Keep prospective overruling for what courts do to their own precedent. And keep proactive for policy and administration, where it earns its place. The words look alike; the burden each places on a client is not.