I understand the due date for SEP contributions is the tax filing due date and/or extensions. When extended, am I correct that the contribution is due by the extended date irrespective of when the extended return is actually filed? Example: Sole prop return is extended, but the CPA files in June. My understanding is that the SEP contribution can still be made after the return is filed so long as the contribution is made prior to 10/15. Is that right?