Passive forms with modal verbs

Definition

A modal passive uses modal + be + past participle to combine passive voice with meanings such as possibility, necessity, permission, prediction, or obligation. A past modal passive can use modal + have been + past participle.

Examples

• The form must be signed today.

  The modal expresses obligation, and the form receives the action.

• The meeting may be postponed.

  The passive construction expresses a possible future change.

• The keys might have been left at reception.

  The speaker considers a past passive event possible.

Active vs. passive after a modal

The passive version moves the affected person or thing into subject position and may omit the agent.

Past modal meaning uses have been

To refer to a possible, expected, or necessary passive event before the present, use modal + have been + past participle.

• The parcel may have been delivered already.

  The speaker considers an earlier delivery possible.

• The warning should have been issued sooner.

  The sentence evaluates an earlier passive action that did not happen at the appropriate time.

Common mistakes