Say the amendment is just to incorporate the missing deductions (equipment purchases recorded as equity), that will bring down the 2020 - 2021 schedule C income, say we do not elect it as an S-Corp.  The SEP IRA contribution made would become excessive as a result of amending the tax return. 

If we convert the SEP IRA to a qualified 401(k) plan in 2022, does that change the excessive SEP IRA contribution in prior years?