| Positive |
|||
| Modal | Past | Future | |
| 1a | Must | Cannot use must Use rule 2a | Cannot use must Use rule 2a |
| 2a | Have to | had to | will have to |
| 3a | Need to | Needed to | will need to |
| 4a | Should | Should have | should |
| 5a | Ought to | Ought to have | ought to |
| 6a | be allowed to | were allowed to | will be allowed to |
| 7a | Can | could | Cannot use can Use rule 6a |
| Negative | |||
| Modal | Past | Future | |
| 1b | Must not | Cannot use must Use rule 6b | Cannot use must Use rule 6b |
| 2b | Do not have to | did not have to | will not have to |
| 3b | Need not/ do not need to | did not need to | will not need to |
| 4b | Should not | Should not have | should not |
| 5b | Ought not to | Ought not have | ought not to |
| 6b | Not allowed to | were not allowed to | will not be allowed to |
| 7b | Cannot | Could not | Cannot use cannot Use rule 6b |