I had a solo 401(k) that had a plan termination date of 12/31/21. All assets were distributed as of 3/21/22. To avoid the successor rule, I waited more than 12 months before establishing a new plan. I signed the adoption agreement for a new 401(k) on 12/12/23 but, following guidance on the application to typically have an effective date as of the start of the plan year, I put an effective date of 1/1/23. I realize now that perhaps this effective date should have been 3/22/23 or later to be a full year after 3/21/22.
For purposes of the successor rule, does the effective date matter or just the adoption date? If the effective date is wrong, how can I proceed? File an amendment? Shut down and make a new one? There are no assets in the account yet.
