10/15/2026 (11:59 PM ET). Betterment’s 2025 SEP contribution deadline.

If you filed an extension and wish to contribute to your 2025 SEP IRA by the 10/15/2026 tax filing deadline, you must initiate your deposit through Betterment by 11:59 PM ET on 10/15/2026, to ensure that your contribution completes by the deadline.