I have a Roth Solo 401K. Each year my income is about the same. I was wondering if I can put into my account what I normally put in for the year early (3/15/23)?

As long as I am not over the amount I am allowed to put in by the end of the year (12/31/23) would I be ok? Am I able to do this?

The following year can I put in the money 1/1/24? What the earliest or the rules regarding putting money into the account?

Thanks so much for your time! I really appreciate it!