The verb phrases have to and have got to express necessity and obligation. They differ subtly in meaning from the auxiliary verb must. While all of these verbs can be used to express a command or warning (You have got to leave now. You must not shout), have to and have got to are somewhat more forceful than must in expressing necessity. There has (or has got) to be some mistake conveys a bit more emphasis than There must be some mistake. Only have to can form verb phrases with may, be, and have. We can say I may have to go but not I may have got to go. We can say You are having to do a lot more work these days but not You are having got to … We can say The town has had to repave its main road but not The town has had got to … In spoken English people often drop the have from have got to, as in We got to get up early. But in formal writing got to is not ordinarily considered acceptable.
