Could/Might have been doing: possible activity and unrealised scenarios

1. One form, two questions

Could/might have been + -ing combines possibility with a view of an activity in progress. But possibility can mean different things: “Might this actually have been happening?” or “What could have been happening under different circumstances?” Context determines the reading; the form itself does not say that the action definitely happened or definitely did not happen.

When speculating, we do not know the facts. In an alternative scenario, we may know that someone made a different choice. Do not turn every speculation into a conditional sentence: uncertainty does not require a hidden if.

How to build it

subject + could / might + have been + -ing verb

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.
verb / V: A word for an action or state, such as work or be. The pattern determines its form.
V-ing / -ing: The verb form ending in -ing: working, going. Its role depends on the construction.

Rita might have been recording a lesson when you called.

We do not know what she was actually doing. Recording a lesson is one possible activity at the time of the call; the sentence does not say whether she answered.

Rita declined the project. She could have been recording lessons all summer.

The refusal establishes an unrealised possibility: if she had accepted. This is not a guess about how she actually spent the summer.

2. The fixed sequence and word order

After could or might, use have, not has or had; then been, followed by the -ing form of the main verb. The subject does not change this sequence. Do not add to or did.

In a direct question, the modal verb goes before the subject: Could she have been working? Might she have been working? The second is possible but sounds more formal. In an embedded question, keep subject + modal order: Do you think she might have been working?

How to build it

Question: Could / Might + subject + have been + -ing? Negative: subject + might not / could not + have been + -ing.

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.
V-ing / -ing: The verb form ending in -ing: working, going. Its role depends on the construction.

Could the neighbours have been moving furniture?

Could the neighbours have been moving furniture at that time?

Could moves before the subject; the remaining sequence stays have been moving.

Do you think the neighbours might have been moving furniture?

Do you think the neighbours might have been moving furniture at that time?

After Do you think, use the normal order the neighbours might, without a second inversion.

3. Speculation: a sign is not proof

Could have been working and might have been working can both present past activity as possible. There is no universal scale on which could is always more certain than might. Context, stress and the speaker's habits affect the nuance; do not assign fixed percentages to these words.

Lights, tiredness or an open document may suggest an explanation, but they do not prove it. Add a check or another possibility if the facts are unknown. Do not infer someone else's intentions solely from an outward sign.

The studio lights were on. Someone could have been editing a video, but the timer may simply have failed.

The speaker is considering an explanation, not announcing an established fact.

Nina might have been waiting at the side entrance; I only checked the front door.

The incomplete check leaves room for a possibility. No unreal condition is needed here.

4. An alternative past: a possibility, not a promised result

For an unrealised past condition, the usual frame is if + had + V3, with could/might have been + -ing in the result clause. Could often highlights an available opportunity or capability; might highlights one possible consequence. This is not a mechanical difference in percentages of certainty.

The condition may be stated directly or understood from the conversation. Its absence alone does not determine the reading, however. In an unrealised scenario, the circumstances allow us to understand an “if…” condition; in an ordinary guess about facts, we do not need to reconstruct one.

How to build it

If + subject + had + V3, subject + could / might have been + -ing

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.
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.
V-ing / -ing: The verb form ending in -ing: working, going. Its role depends on the construction.

If we had rented the upstairs room, we could have been teaching two groups at once.

The additional room would have made simultaneous work possible; the sentence does not guarantee that students would necessarily have enrolled.

We cancelled the outdoor workshop. Otherwise, we might have been working in the rain all afternoon.

Otherwise refers to the alternative “if we had not cancelled”. The speaker imagines a possible course of events.

5. Process, duration and result are different

Have been + -ing shows activity in progress, sustained work or repeated work over a period. A completed result often needs could/might have + V3. Both forms can be grammatical in the same situation, but they answer different questions.

The continuous form guarantees neither completion nor continuation now. Context specifies the time and boundaries. State verbs, such as know in the sense of being familiar with someone, are normally used without the continuous; duration alone does not require -ing.

They might have been repairing the lift that morning.

The focus is on the repair process. We are not told whether the lift was repaired.

They might have repaired the lift before lunch.

This speculates about a completed result. It is a different perspective, not an error.

He might have known the organiser for years.

Known expresses the state of knowing someone. For years does not make the continuous compulsory.

6. Might not and couldn't: different negatives

Might not have been doing usually means that it is possible the activity was not happening: its absence is merely a possibility. Couldn't have been doing, when drawing a conclusion about facts, means that the activity was impossible: the speaker rules out that explanation.

But couldn't can also describe a lack of capability or opportunity under particular circumstances. Do not automatically interpret it as a strong deduction. First establish whether the speaker is assessing the truth of an explanation or the availability of an activity.

Leo might not have been listening when the date was announced.

Inattention is only one explanation; the sentence does not prove it.

Leo couldn't have been using that computer at noon: it was unplugged and had no battery.

The stated conditions rule out the use of that particular device at the specified time.

Without the loan, we couldn't have been running the café that winter.

This describes how the ability to operate depended on funding, rather than suggesting that the café was actually closed.

7. Boundaries: would, a present reference point and a future perspective

Would have been doing is also a modal construction. In a conditional scenario, it presents the expected consequence if the condition is accepted, whereas could/might leave room for possibility or uncertainty. A condition can be unspoken with would too; this is not a feature unique to could/might.

The main focus of this lesson is past processes and an alternative past. However, have does not mean “exclusively before the moment of speaking”. The perfect looks back from a reference point that may be present or future, and a duration may extend up to that point. This marks the boundary of the rule; it is not a separate course on future forms.

I turned down the night shift. I would have been working alone.

The conversation makes the condition clear: if I had accepted. Would presents working alone as the expected consequence, not as proof that it happened.

If I had joined in January, I could have been working here for eight months by now.

The unrealised duration extends to by now; it does not necessarily end in the past.

Ask her tomorrow. By then, she might have been working on the problem for a week.

Tomorrow / by then establishes a future reference point. This applies the general principle of the modal perfect to an extended process.

8. Formulating your own idea

First separate the fact from the possible explanation. Then decide whether you are describing unknown real activity or an alternative to a different decision. Finally, decide whether the process matters, and specify the time if the listener does not already know it.

In open exercises, the model is only one natural option. Check meaning, form, limits of certainty and communicative purpose; synonyms and appropriate variations in word order are allowed. All situations may be imaginary. Self-checking helps identify differences, but it is not an automatic language assessment.

I found several drafts, so the team might have been testing different titles. I'll ask them before changing anything.

The fact, cautious explanation and next action are kept separate. Speculation does not replace checking.

If we had shared the preparation, I could have been helping guests instead of carrying boxes.

The sentence names a specific alternative activity and the condition that would have made it possible.

Common mistakes

Incorrect:She might has been editing the notes.

Correct:She might have been editing the notes.

After might, use the base form have, regardless of the subject she.

Incorrect:We could have be waiting outside.

Correct:We could have been waiting outside.

The perfect sequence requires been, not be.

Incorrect:He could have been repair the door.

Correct:He could have been repairing the door.

To describe the process, use the -ing form repairing after been.

Incorrect:Did they might have been working late?

Correct:Might they have been working late?

Might itself forms the question; do not add did.

Incorrect:The tutor might of been preparing another lesson.

Correct:The tutor might have been preparing another lesson.

In writing, the perfect sequence contains have, not the similar-sounding of.

Sources