Which one is correct May I request a copy of your catalogue May I request a copy of your catalogue?

Both are grammatically correct, both are exactly the same except for the question mark at the end of your question, which belongs on the end of the sentence.

May I request a copy of your catalogue

May I request a copy of your catalogue?

A suggestion for actually using this sentence in business writing; the answer to the question is yes or no, which is not the same as fulfilling a request for a copy of the catalogue. Business writing must clearly say what you want. Some alternative sentences:

I am writing to request a copy of your catalogue...

Please send a copy of your catalogue to ...