This topic covers two ideas: things that are not necessary, and things that are expected. Americans mostly say don't need to or don't have to for the first, and be supposed to for the second. You will still meet needn't and be meant to in books and British English, so it helps to recognize them.
The pattern
You don't need to print your ticket.
You're supposed to tip about 20 percent.
The package was supposed to arrive yesterday.
01Not necessary: don't need to, don't have to
In American English, the everyday way to say something isn't necessary is don't need to or don't have to. They mean almost the same thing. Needn't exists, but Americans rarely say it. It sounds formal or British.
Careful: don't have to (it's not necessary) is very different from must not (it's not allowed).
- You don't need to bring anything. We have plenty of food.
- We don't have to wear suits on Fridays.
- You must not share your password with anyone.
02The past: didn't need to and needn't have
For the past, Americans say didn't need to or didn't have to. Usually this means it wasn't necessary, so it didn't happen. Add context if it happened anyway: "I didn't need to bring cash, but I brought some just in case."
British English also has needn't have + past participle, which always means you did it, but it was unnecessary. In American English, say didn't have to. "Oh, you didn't have to!" is also the classic thing to say when someone gives you a gift.
| Meaning | American English | British (recognize only) |
|---|---|---|
| Not necessary, so we didn't | We didn't need to cook. | We didn't need to cook. |
| We did it, but it was unnecessary | We didn't have to cook, but we did. | We needn't have cooked. |
03Be supposed to: rules and expectations
Be supposed to says what a rule, a plan or other people expect. Someone else decided, not the subject. It is softer than must and often hints that people don't always follow the rule. It can also report what people say: "It's supposed to be good" means people say it's good.
- You're supposed to take your shoes off at the door.
- Am I supposed to sign here?
- The new Thai place is supposed to be great.
- It's supposed to rain tomorrow.
04Was supposed to: plans that didn't happen
Was or were supposed to usually means a plan or an expectation that failed. Wasn't supposed to means something happened that shouldn't have, like a secret getting out.
- I was supposed to fly home Friday, but the flight was canceled.
- We were supposed to meet at noon.
- You weren't supposed to tell her about the party!
05Be meant to
Be meant to is close to be supposed to. Americans use it mostly for purpose ("This app is meant to help you save money") or destiny ("We were meant to be together"). For everyday rules, supposed to is the natural American choice.
- This knife is meant for cutting bread.
- The surprise was meant to stay secret.
06Common mistakes
You must not bring anything. We have plenty of food.
You don't need to bring anything. We have plenty of food.
Must not means it's forbidden. For not necessary, use don't need to or don't have to.
I'm suppose to call my mom tonight.
I'm supposed to call my mom tonight.
Always write supposed with a d, even though you can't hear it.
We supposed to meet at noon.
We were supposed to meet at noon.
Supposed to needs a form of be: am, is, are, was or were.
I didn't needed to pay.
I didn't need to pay.
After didn't, use the base form need.