That's a good question and one I could not find addressed in the Reg. or the GIR. I know of no reason why it could not be submitted early but, you should contact your regulator, not HMDA Help, and ask them. It will be my guess they will instruct you to wait until Jan 1st.
Let us know what you find out.
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The opinions expressed are mine and they are not to be taken as legal advice.