You can make contributions between January 1 and April 15 that are either intended and designated for the current year, or are designated for the previous year. To designate a contribution for the previous year, you must tell the plan in advance that you are doing that, usually with a menu selection on a web site or with a form you send with a paper check if you make deposits by check.
If you plan to make contributions in 2025 that are designated for 2024, report them now. If you plan to make contributions in 2025 that are intended for 2025, don't report that now.
