I have confusion about using did in questions ?

a ) Let me know when did we change this ?

b ) Let me know when we changed this?

Both sound correct to me .

Is there any rule about useing did in english questions?

  • You confuse the issue by including the words Let me know before the "question". We often follow those words with a syntactically valid question such as When did we change this? (with "do-support" and subject+verb inversion, as is the standard for questions in English), but idiomatically we also often just retain the normal word order appropriate for a noun phrase (as typically used within a statement). Note that the second version doesn't work unless preceded by something like I want to know... (so When we changed this? is invalid, although it's common coming from nns). Aug 28, 2018 at 14:34
  • "Let me know..." is grammatically an imperative, not a question.
    – stangdon
    Aug 28, 2018 at 15:14

2 Answers 2


A question:

When did we change this?

A request:

(Please,) Let me know when we changed this.

A request, combined with a question:

Please, let me know the following: when did we change this?

So, for correct word order it is important to choose a form (a question, a usual sentence or something more complicated).


To my BrE ears the first two sentences have slightly different meanings. The first question:"When did we change this?" conveys an aggressive tone, as if the boss is asking his subordinates why something he always thought was X is now not-X. It is obviously less aggressive than "when did you change this?" but it is aggressive, nonetheless.

The second question is more nearly neutral, but if I were a subordinate and the question was asked by my boss, I should be a little nervous.

The third is just a longer way of asking the second question.

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