thank you is correct.
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Anonymousthankyou adjective expressing gratitude
thankyou noun anything expressing gratitude (esp a gift)
Sorry, but no. These are written as two words.
If you want to use them as adjectives or nouns, use a hyphen.
Did you write your thank-you notes?
Make sure you say your thank-yous to your host and hostess before you leave. (This
AnonymousThankyou has always been the correct form of thanking somebody, (in Britain)It has never been correct. as a way of thanking somebody.