Future subjunctive for uncertain future events

In brief

Use the future subjunctive for an event that may happen later, especially after quando (when), assim que (as soon as), or se (if). The dependent event is still uncertain; the main clause says what will happen if or when it does.

Form

Take the third-person plural simple past, remove -am, and add -Ø, -es, -Ø, -mos, -des, -em: falaram → falar, falarmos; tiveram → tiver, tivermos; fizeram → fizer, fizerem. Regular singular forms often look like the infinitive.

Usage

• After quando or assim que, use it for a future event that has not happened yet.
• After se, use it for a possible future condition; do not use the future indicative in that clause.

Examples

• Quando você tiver tempo, me avise. — When you have time, let me know.
• Assim que eles fizerem o pagamento, enviaremos o recibo. — As soon as they make the payment, we’ll send the receipt.
• Se ela puder, vai participar da reunião. — If she can, she’ll attend the meeting.

Common mistake

❌ Quando você terá tempo, me avise.

✅ Quando você tiver tempo, me avise.

For a future time that is not yet certain, quando takes the future subjunctive tiver, not the future indicative terá.

Remember

Some common verbs change their stem: ter → tiver, fazer → fizer, poder → puder.