Grammar rule and drill

Future time clauses: when, before, after, until

When, before, after, as soon as and until take the present, even when the meaning is future.

CEFR B1-B220 questionsUpdated 5 October 2026

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Future time clauses are the sentences that begin with when, before, after, as soon as, until, once or while. They describe the moment at which something else will happen: "I will call you when I arrive."

The rule that surprises learners is simple: the time clause does not take will. It takes the present simple, even though the meaning is future. Will belongs in the main clause, or disappears when the sentence does not need it.

This page explains why, shows the words that follow the rule, and covers the main clause patterns that go with it: will, going to, the present continuous, can and the imperative. The drill has 20 questions with a reason printed under each answer.

The rule

The central rule: present in the time clause

Pattern: when, before, after, as soon as, until, once or while plus the present simple.
"I will call you when I get home." Not "when I will get home".
The present form does not mean present time. It means the event is not finished yet, so it stays outside the will clause.
The same rule applies to if-clauses in the first conditional: "If it rains, we will stay in."

The main clause can be many things

Will: "She will text us as soon as she lands."
Going to: "We are going to start after everyone arrives."
The present continuous: "I am meeting Tom when the film ends."
The imperative: "Before you leave, turn off the lights."
Can, may or should: "Once you finish, you can go home."

Which word to choose

When marks the moment something happens: "When the film ends, we will walk home."
As soon as makes the link immediate: "Call me as soon as you hear anything."
Before and after put the events in order: "Wash your hands before you eat", "After the guests leave, we will tidy up."
Until or till marks the end point of a wait: "Stay here until I come back."
Once means "after the moment when": "Once the rain stops, we can play outside."

For actions completed before a future point

By the time plus the present perfect shows an action finished before a future moment: "By the time you read this, I will have left."
The present perfect is possible after when for a completed action: "When I have finished the report, I will send it to you."
The present simple still works in most of these sentences: "When I finish the report, I will send it."
Use by the time for deadlines, and at the time for moments that are not deadlines.

Common mistakes to watch

Never put will directly after when, before, after, as soon as, until or once.
Do not forget the main clause. A time clause on its own cannot stand as a sentence.
Remember the third person -s in the time clause: "when she arrives", not "when she arrive".
With if, stay in the same pattern: "If you hurry, we will catch the train."
While takes an action in progress: "While you are shopping, I will cook."

Examples

I will call you when I get home.The time clause uses the present simple get, although the meaning is future.
As soon as she arrives, we will leave.As soon as introduces the future moment in the present simple.
We will not start until everyone is here.Until marks the end of the wait; the clause stays in the present.
Before you leave, turn off the lights.The main clause is an imperative, so it needs no will at all.
After he finishes his homework, he will play outside.The order of the two events is clear from after.
I will wait here while you buy the tickets.While takes an action in progress during the wait.
By the time you read this letter, I will be in Rome.By the time plus the present simple marks the future deadline.
If it rains tomorrow, we will cancel the picnic.If follows the same rule as the time words. No will in the if-clause.
Once the rain stops, we can play outside.Once means after the moment when. The main clause uses can.
She will text us as soon as she lands.A typical travel sentence with as soon as.

Common mistakes

Wrong: I will call you when I will get home. Right: I will call you when I get home.: The time clause takes the present simple, not will, even when the meaning is future.
Wrong: After the meeting will end, we will go for lunch. Right: After the meeting ends, we will go for lunch.: After introduces a future time clause, so the verb stays in the present simple.
Wrong: When she will arrive, tell her to wait. Right: When she arrives, tell her to wait.: Will never goes directly after when in this pattern. The present simple carries the future meaning.
Wrong: I stay here until you will come back. Right: I will stay here until you come back.: Will belongs in the main clause, not after until. The time clause keeps the present simple.
Wrong: If it will rain, we will cancel the picnic. Right: If it rains, we will cancel the picnic.: If-clauses follow the same present-tense rule as other future time clauses.

Questions learners ask

Why does English use the present for the future in these clauses?

The will in the main clause already marks the sentence as future. English does not repeat the marker inside the time clause. The present form in the clause means "at the moment this happens", and the main clause supplies the future. The same pattern appears with if: one future marker is enough.

Can I use the present perfect after when?

Yes, when the first action must be complete before the second one starts. "When I have finished my work, I will call you" emphasises the completion of the work. The present simple is also correct and is more common in speech: "When I finish my work, I will call you."

What is the difference between until and by the time?

Until marks how long a situation continues: "I will wait until you call." By the time marks a deadline that another action has already reached: "By the time you call, I will have gone home." Until looks forward to a moment; by the time looks back from a future moment.