Q: "Do I need to include an ISBN number when sending my book to copyright for registration?"
R: No. The copyright registration will cover your book even if it does not have the ISBN published within.
The above response is general information ONLY and is not legal advice, does not form an attorney-client relationship, and should NOT be relied upon to take or refrain from taking any action. I am not your attorney. You should seek the advice of competent counsel before taking any action related to your inquiry.
Wrong. You already sent your book to copyright the moment you created it. 17 USC 102.
The publisher gets the ISBN not you.
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.