Solo Proprietor earlier this year funded a SEP-IRA for the 2021tax year
Now (due to an increase earnings) he wants to fund a Solo 401(k) – because he will be able to contribute the max @ $58,000 which he won’t be able to with the SEP

I am a you can’t fund both a SEP and Solo $401(k) in the same tax tax assuming the SEP was established using IRS Form 5305-SEP. That being said, what options, if any does the owner have in reversing/canceling the SEP contributions? And instead fully funding the Solo(k) for 2021?

Thank you in advance