Expressing lost opportunity
We can use modals to talk about possibility or advisability in the past. Sometimes these modals are referred to as modals of lost opportunity. They include should have, ought to have, and could have.
I should have done my homework. (I didn’t do my homework, and now I regret it.)
I ought to have written a longer essay. (The essay I wrote is too short, and now it’s too late to write more.)
We could have bought this house. (We didn’t buy this house, but it was possible.)
Remember, the main verb in this kind of construction is in its past participle form (done, eaten, seen, written, etc.). It is not correct to say *I should have did my homework.
Joanna Rodzen-Hickey has been an ESL teacher and consultant for nearly 20 years. She has taught English at numerous universities and community colleges in New Jersey and currently teaches at the Hackettstown High School in Hackettstown, NJ.