When I do / When I've done

Present Simple After “When” for the Future

A sentence about the future often has two parts: the main clause and a time clause starting with when.

• I’ll call you again later when I arrive. (not when I will arrive)

The time is future (“later”), but the verb after when is present simple, not will.

Rule: After when, use do/does — not will — for future meaning.

• We’ll go out when it stops raining. (not when it will stop)
• *When you are here again, you must come and see us.* (not when you will be)
• Don’t forget to lock the door when you go out. (not when you will go)

The Same Rule After While, Before, After, As Soon As, Until

This is not just about when. The same thing happens after while, before, after, as soon as, and until (or till).

Time word	Example
while	What are you going to do while I‘m away? (not while I will be)
before	*Before you go, there’s something I want to ask you.*
until / till	Wait here until I come back.
as soon as	I’ll send the report as soon as I finish it.

In every case, the verb in the time clause is present — even though the meaning is future.

Present Perfect After When / After / Until / As Soon As

You can also use the present perfect (have done) after these time words. Use it to show that one thing must be complete before the other starts.

• Can I have the newspaper when you‘ve finished with it?
• Don’t say anything while Ian is here. Wait until he has gone.
• *When I‘ve phoned Kate, we can go out.* (= first I’ll phone Kate, and after that we can go out)

Do not use the present perfect if the two things happen at the same time:

• *When I phone Kate, I’ll ask her about the party.* (not when I’ve phoned)

Present Simple or Present Perfect — Both OK?

Often either one works. The meaning is almost the same.

Present simple	Present perfect
I’ll come as soon as I finish.	I’ll come as soon as I‘ve finished.
You’ll feel better after you have something to eat.	You’ll feel better after you‘ve had something to eat.

Use the present perfect when you want to stress that the first action is fully done before the second begins.

If and When — What’s the Difference?

After if, use the present simple for the future too — just like when.

• I’ll be angry if it happens again. (not if it will happen)
• Hurry up! If we don’t hurry, we’ll be late.

But if and when do not mean the same thing.

Use if …	Use when …
… for things that will possibly happen (or not)	… for things that are sure to happen
*If it is raining this evening, I won’t go out.*	*When I go out, I’ll get some bread.* (I’m going out — that’s certain)
Don’t worry if I’m late tonight.	*When you see her again, say hello from me.* (you will see her — that’s certain)
*If they don’t come soon, I’m not going to wait.*	*When the contract expires, we’ll need to renegotiate.*

Compare these two:

• I might go out later. If I go out, I’ll get some bread. (it’s only possible)
• I’m going out later. When I go out, I’ll get some bread. (it’s definite)

Summary Table

Structure	Tense after time word	Example
when + future meaning	present simple	I’ll email you when I get to the office.
when + completed first	present perfect	I’ll email you when I‘ve finished the draft.
if + possible event	present simple	*If the client calls, take a message.*
before / after / until / as soon as	present simple or present perfect	Wait until the manager arrives / has arrived.

Quick Self-Check