Learn English – Gerund or infinitive? “Thank you for letting me know” or “Thank you to let me know”

infinitive-vs-gerund

I'm finishing a letter to a friend by asking the tracking number of a parcel he sent to me. Can I finish my letter with

Thank you for letting me know the tracking number

OR

Thank you to let me know the tracking number

Best Answer

If you want to request [something], you would probably not use "Thank you" at the start of the sentence. It is possible to make a request and start a sentence in this way, but it might be construed as a little rude because you are essentially giving a command but hiding it in the form of gratitude.

The other option that Ronald Sole proposes in his comment is valid, but I think it is a little formal (even haughty), especially for a letter between friends.

You'd be better off saying something like:

... and if you would send me the tracking info when you get the chance, I would appreciate it.

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