Opening a SEP IRA for my single member LLC (I am sole owner and employee) to make a 2023 contribution. Since first SEP IRA I’ve opened, I’ve decided to implement my custodian’s plan agreement. The plan agreement is asking for the “plan effective date”. I’ve narrowed it down to any of the below 3 options but can’t seem to figure it out.
1) date that I sign the SEP adoption agreement.
2) 01/01/2024. I’ve seen guidance online that the effective date is the first day of the plan year that the SEP plan agreement is adopted.
3) 01/01/2023. To include calendar year 2023 since I am making a 2023 contribution.

Any guidance here on effective date would be great! Unsure if putting the wrong effective date on the plan agreement would invalidate the 2023 contribution. Thanks so much!!