Which one is correct and why
When did you bought the sim card?
When did you buy the sim card?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
The auxiliary verb "do" is followed by the bare infinitive (which is the same as the base form of the verb).
"She goes" becomes (in an emphatic statement) "she does go" (so, "does" is inflected for person and number, but "go" is a bare infinitive).
It becomes, in the negative, "she doesn't go", and in a question, "does she go?". In the past, "did she go?".
Hence, if you want to ask when someone bought a SIM card, you have to ask "When did you buy the SIM card?".