If less than the full amount contributed was deductible because you contributed more than permitted, the excess amounts are subject to a 10% penalty each year that the excess remains. Such an excess contribution is reportable on Form 5330, a form not supported by TurboTax.
As mentioned by others, if the entire amount contributed for 2020 (or earlier) was deductible but you failed to deduct the entire permissible amount, it's too late to amend your 2020 (or earlier) tax return to obtain a refund of the taxes that were paid unnecessarily. You are not permitted to report SEP contributions on a tax return for a different year than the year for which the contribution was made. The deadline to obtain a refund for 2021 and later has not yet passed. Permissible SEP contributions for with you simply failed to take the deduction do not create basis in nondeductible traditional IRA contributions.
