Need not + have + past participle
If we say that somebody need not have done something, we mean that he or she did it, but it was not necessary.
- You need not have woken me up. I don’t have to go to work today.
- I needn’t have cooked so much food. Nobody was hungry.
- They need not have come all this way. (= They came all this way, but it was not necessary.)
- We need not have waited for his approval. (= We waited for his approval, but that was not necessary.)
- You need not have bought a new car.
- You need not have paid for that call.
Note that need not have does not mean the same as did not need to. When we say that somebody did not need to do something, we are simply saying that it was not necessary (whether or not it was done).
- I need not have bought it. (=I bought it, but it was not necessary.)
- I didn’t need to buy it. (=It was not necessary for me to buy it.)
Need + participle
In British English it is possible to use an –ing form after need. It means the same as a passive infinitive.
- Your hair needs washing. (= Your hair needs to be washed.)
- The carpet needs cleaning. (= The carpet needs to be cleaned.)
- The roof needs repairing.
A structure with need + object + present/past participle is also possible in some cases.
- You need your hair cutting/cut.
- You need your car cleaned.