Savings for All Vocations Enhancement Act of 2021 or the SAVE Act of 2021 This bill modifies provisions relating to tax-exempt retirement plans. It (1) allows employers who establish a tax-exempt 403(b) pension plan to participate in a multiple employer plan, (2) allows employers who join an existing pension plan to take the tax credit for small employer pension plans start-up costs, (3) makes certain findings relating to S corporation employee stock ownership plans (ESOPs), (4) reduces the excise tax on certain accumulations in tax-exempt retirement plans and on failures to take required minimum plan distributions, and (5) sets forth a statute of limitations rule for purposes of the excise tax on excess plan contributions and accumulations in connection with an individual retirement plan.