Conjugation and verb forms of modal auxiliary verbs in the past simple

(Formation of the past simple of the modal verbs: can, must, may, used to, ought to)

Formation of the past simple of modal auxiliary verbs (can, must, may, used to, ought to)

The following modal auxiliary verbs have unique forms in the past simple, which may sometimes differ in meaning. Compare the following example sentences as well as the use in the table below:

Examples of the auxiliary verbs ‘can, must, used to, ought to’ in the past tense as they may occur in a sentence:
- “When Jim was a child, he could speak Italian fluently.”
- “The policeman said I had to get out of the car.”
  - Be careful when using ‘must’ – it becomes ‘had to’.
Information: Refer to present simple of modal verbs for present tense forms.

Verb forms of ‘can, ought to, must, used to, may’ in the past simple

The column ‘Past Simple’ shows the proper forms of the modal verbs. Not every modal verb has such a form.

Note: Although the substitute form represents the past of the respective modal verb, there may be a (slight) difference in meaning to the normal forms.

Modal verb	Past simple	Possible substitute or alternative form in the past
can	could	was/were able to
must	–	had to or had got to (British English)
may	might	was/were allowed to
used to	used to	–
ought to	ought to	–

Examples and particularities of the modal verbs ‘can, ought to, must, used to, may’ in the past simple

The following example sentences show the use of the modal verbs in the past (simple). Consider the particularities, which some modals offer:

‘can’ has ‘could’ in the past simple and the substitute form ‘was/were able to’; examples:
- “He could easily win every race when he was young.”
- “I was able to get in without a ticket.”
  - There is a slight difference in meaning between both forms. See ‘can’ and ‘be able to’ to learn the details.
‘must’ can form the past simple only with the alternative form ‘had to’ or ‘had got to’:
- “I had to pay the bill.”
- “She received an emergency call and had got to go early.”
‘may’ has the substitute form ‘was/were allowed to’ or the actual past ‘might’:
- “We were allowed to pass.”
- “She said she might move to Australia.”
  - ‘may’ can also become ‘might’ for grammatical reasons (see the difference ‘may/might’).
‘used to’ (consult ‘used to’ for the usage in detail). Note that this form is neither possible nor does it exist in the present tense:
- “I used to go jogging every day.”
- “He didn’t use to go out.”
- “We used not to go to parties.”
‘ought to’ is only occasionally utilized; in most cases, ‘should’ is preferred instead:
- “We ought to get home early.”
- “This ought to be enough.”
- “They ought to study the language.”

Further explanations related to the ‘Formation of modal verbs in the past simple’

The following explanations relate to the topic ‘Conjugation and verb forms of the past simple of ‘can, used to, ought to, must, may’’ and could also be interesting:

Past simple: conjugation of modal verbs