A schedule, not probability
Be due to means that an event is expected at a particular time according to a schedule, timetable, or arrangement. The speaker is not assessing the chances or guessing: the time has already been set, and the construction simply reports it.
The time is often stated directly: at 6:30, next week, shortly. But it may be clear from context; The director is due to retire is a complete sentence about a planned retirement that is expected to happen.
The ambassador is due to land at half past six.
The ambassador is due to land at half past six.
The arrival time is set by the schedule; the speaker is reporting the plan, not guessing.
I'm due to see the dentist on Thursday.
I'm due to see the dentist on Thursday.
The dental appointment is an arrangement, so be due to is appropriate.
The new bridge is likely to open late.
The new bridge is likely to open late.
This expresses an assessment of probability (be likely to), not a schedule; for a schedule, we would say is due to open.
Form: be + due to + verb
The construction has the form subject + am/is/are/was/were + due to + the base verb. After to, never use -ing and do not add -s: due to arrive, not due arriving or due to arrives.
If the subject receives the stated action, use the passive infinitive due to be + V3: The results are due to be announced. An inanimate subject does not make the passive obligatory: The parcel is due to arrive has the ordinary active verb arrive.
subject + am/is/are/was/were + due to + V1 (+ time) / due to be + V3
- subject / S —
- The grammatical subject: who or what the clause is about; the verb agrees with it. In The book was written, the book is the subject, although someone else does the action.
- V1 / base form —
- The base verb without to: work, go, be.
- V3 / past participle —
- The third verb form: worked, gone, seen. Used after have/has or in the passive, for example; it is not always the same as V2.
The tenants are due to move in on the first of June.
The tenants are due to move in on the first of June.
The subject is plural, so use are; after due to comes the base form move.
The prize is due to be awarded after the speeches.
The prize is due to be awarded after the speeches.
The prize is awarded to someone, so use the passive infinitive be awarded.
Negatives, questions, and time markers
Put the negative on be: isn't due to, aren't due to. Together with until or before, this means “not earlier than”: the event is not expected before a particular time.
In questions, be comes before the subject: When are the builders due to finish? The auxiliary do is not needed. Time markers such as any minute, shortly, and soon strengthen the meaning “very soon.”
The doctor isn't due to see patients until two.
The doctor isn't due to see patients until two.
The negative on be together with until sets a boundary before which the appointments are not expected.
When are the builders due to finish?
When are the builders due to finish?
In the question, are comes before the subject; do is not used.
The speaker is due to arrive any minute.
The speaker is due to arrive any minute.
Any minute is a time marker meaning “very soon” used with the construction.
A past plan that may not have happened
The past forms of be (was/were due to) report a plan that existed earlier. Whether it happened depends on the context: often but follows, revealing that the event was delayed or cancelled.
Therefore, use was due to when you want to say “was planned to happen”; do not use is due to with a time that has already passed.
The festival was due to start on Friday, but the permit arrived late.
The festival was due to start on Friday, but the permit arrived late.
Was due to names the plan; but shows that it did not happen on time.
We were due to meet at six, but I stayed late at the office.
We were due to meet at six, but I stayed late at the office.
Were due to names the earlier arrangement. Staying late at the office interfered with the plan, but the sentence itself does not specify whether the meeting happened later.
Boundaries: due to + noun, be due + time, and related expressions
Due to + a noun phrase can mean “because of”: The delay was due to a faulty signal. An -ing form is also possible for a cause: due to being short of staff. In the scheduling pattern, the base form follows due to: due to arrive.
The shorter form be due + time is also possible: The rent is due on the first; Her baby is due in August. It puts the deadline at the center, and the verb disappears. Be likely to and be bound to express probability and near certainty, not a schedule; they are covered in related rules on this topic.
The delay was due to a faulty signal.
The delay was due to a faulty signal.
Due to + a noun expresses a cause; there is no schedule meaning here.
The rent is due on the first.
The rent is due on the first.
Be due + time without to and a verb names a deadline.
Using it in speech and writing
Be due to is often heard in announcements, work emails, and news reports about schedules, deadlines, and expectations. The tone is neutral and formal, making it suitable for unemotional notices.
In an email, combine the two forms: was due to for the original deadline and is now due to for the new one. Add the reason for the delay in a separate sentence with because of or due to + a noun, so that the meanings are not confused.
The next update is due to go live tonight; please save your work.
The next update is due to go live tonight; please save your work.
A typical work message: an expected time and a request.
Common mistakes
Incorrect:The coach is due leaving at nine.
Correct:The coach is due to leave at nine.
After due, use to and the base form of the verb; an -ing form is not possible here.
Incorrect:The winners are due be announced on Friday.
Correct:The winners are due to be announced on Friday.
You need to between due and be: due to be + V3.
Incorrect:The exam is due to starts at nine.
Correct:The exam is due to start at nine.
After to, use the base form without the -s ending.
Incorrect:The train due to arrive at noon.
Correct:The train is due to arrive at noon.
The sentence needs a form of be before due (is/are/was).
Incorrect:The new library is due to opened in May.
Correct:The new library is due to be opened in May.
The passive infinitive requires be before V3: to be opened.