The Grammaring Guide to English Grammar with Exercises

Modal changes in indirect speech

Similarly to tenses, modals change in indirect speech if the reported words are no longer true or are out-of-date:

Direct speech » Indirect speech

can

(ability, present) »

could

can

(ability, future) »

would be able to

may

(possibility) »

might

may

(permission, present) »

could

may

(permission, future) »

would be allowed to

must

(obligation, present) »

must / had to

must

(obligation, future) »

must / would have to

needn't

(necessity, present) »

didn't have to / didn't need to

needn't

(necessity, future) »

wouldn't have to

shall

(future time) »

would

shall

(offers, suggestions) »

should

will

»

would

The following modals do not change:

could

would

might

must

(deduction)

mustn't

had better

should

ought to

used to