MODALS IN THE PAST
As we have seen, modal verbs are followed by the base form of the verb, without "to":
I can swim.
She should study.
They must leave.
But what happens when we want to use a modal to talk about something that happened — or might have happened — in the past?
👉 We use a special structure:
MODAL + HAVE + PAST PARTICIPLE
These are commonly called past modals.
They can express different meanings about the past, including possibility, probability, certainty, impossibility, advice, regret, expectation and hypothetical situations.
📌 1. SHOULD HAVE — something that was advisable
We use should have + past participle to say that something was the right thing to do in the past, but it didn't happen.
I missed the concert. I should have gone.
Me perdí el concierto. Debería haber ido.
I should have called you.
Debería haberte llamado.
This structure often expresses regret or criticism about a past action.
Negative:
shouldn't have + past participle
I shouldn't have said that.
No debería haber dicho eso.
Here, the action did happen, but the speaker thinks it was a mistake.
📌 2. COULD HAVE — a past possibility or opportunity
We use could have + past participle when something was possible in the past, but it didn't necessarily happen.
We could have taken a taxi.
Podríamos haber tomado un taxi.
You could have asked me for help.
Podrías haberme pedido ayuda.
It can also express a possibility about something that may have happened:
He could have missed the train.
Podría haber perdido el tren.
👉 So, could have can refer either to a possibility that existed or to a possible explanation for a past situation. The context tells us which meaning is intended.
📌 3. MIGHT HAVE / MAY HAVE — past possibility
We use might have or may have when we think something possibly happened, but we are not certain.
She might have forgotten.
Puede que se haya olvidado.
He may have taken the wrong train.
Puede que haya tomado el tren equivocado.
Compare:
He must have forgotten. → I'm quite sure.
He might have forgotten. → It's possible.
📌 4. MUST HAVE — a strong conclusion about the past
Must have + past participle is used when we have evidence and make a strong conclusion about something that happened.
Look at the puddles. It must have rained last night.
Mira los charcos. Debe de haber llovido anoche.
She's exhausted. She must have had a very long day.
Está agotada. Debe de haber tenido un día muy largo.
⚠️ Here, must does NOT express obligation.
Compare:
You must leave now.
Debes irte ahora. → obligation
You must have been very tired.
Debes de haber estado muy cansado. → deduction
📌 5. CAN'T HAVE / COULDN'T HAVE — something was impossible
We can use can't have + past participle to say that, based on the evidence, something could not have happened.
She can't have forgotten. I reminded her this morning.
No puede haberse olvidado. Se lo recordé esta mañana.
He can't have taken the train. The station was closed.
No puede haber tomado el tren. La estación estaba cerrada.
We can also use couldn't have when the context makes the impossibility clear:
He couldn't have taken a walk. It was raining heavily.
No pudo haber salido a caminar. Estaba lloviendo muchísimo.
🔄 PAST MODALS IN PROGRESS
Sometimes we want to talk about an action that was in progress at a particular moment in the past.
In this case, we use:
MODAL + HAVE + BEEN + VERB-ING
He couldn't have been walking in that rain.
No pudo haber estado caminando bajo esa lluvia.
She must have been working late.
Debe de haber estado trabajando hasta tarde.
They might have been waiting for us.
Puede que hayan estado esperándonos.
Compare:
He must have worked late.
→ Debe de haber trabajado hasta tarde.
He must have been working late.
→ Debe de haber estado trabajando hasta tarde.
The second sentence emphasizes the activity in progress.
🔄 PAST MODALS IN THE PASSIVE
We can also use past modals in the passive voice.
The structure is:
MODAL + HAVE + BEEN + PAST PARTICIPLE
My computer should have been repaired by now.
Mi computadora ya debería haber sido reparada.
The documents must have been sent yesterday.
Los documentos deben de haber sido enviados ayer.
The problem could have been avoided.
El problema podría haberse evitado.
Notice the difference:
Active
They should have repaired my computer.
→ Deberían haber reparado mi computadora.
Passive
My computer should have been repaired.
→ Mi computadora debería haber sido reparada.
🧠 ONE STRUCTURE — DIFFERENT MEANINGS
The basic structure stays the same:
MODAL + HAVE + PAST PARTICIPLE
But the modal changes the meaning:
Modal Main idea Example
should have advice / regret I should have called.
could have possibility / opportunity We could have gone.
might have possibility She might have forgotten.
may have possibility He may have left.
must have strong deduction They must have left.
can't have strong impossibility She can't have done it.
would have hypothetical past I would have helped.
⚠️ Don't translate HAVE literally
One of the biggest difficulties for Spanish speakers is trying to translate every word separately.
For example:
I should have gone.
We don't translate have as tener.
The complete structure should have gone means:
Debería haber ido.
Likewise:
She must have forgotten.
Debe de haberse olvidado.
They might have left.
Puede que se hayan ido.
👉 Learn the structure as a whole:
should have + past participle
could have + past participle
might have + past participle
must have + past participle
🎯 QUICK PRACTICE
Choose the most appropriate modal.
I arrived late. I __________ left earlier.
Look at the wet streets. It __________ rained last night.
I'm not sure where Sarah is. She __________ gone out.
You __________ have told me! I could have helped you.
We __________ have taken a taxi, but we decided to walk.
She can't be here. She __________ have gone home already.
If I had known, I __________ have helped you.
He wasn't at the meeting. He __________ have forgotten about it.
Remember:
MODAL + HAVE + PAST PARTICIPLE
should have gone
could have gone
might have gone
must have gone
👉 The modal tells us how the speaker views the past situation: as advice, a possibility, a strong conclusion, an impossibility, a hypothetical situation, etc.
SOME PRACTICE