No. July 4, 2026 is when the account activates, not a one-time deadline. Enrollment is open now. You can submit the form today, and accounts activate on July 4, 2026. After that date you can enroll at any point before the end of the calendar year your child turns 18. Missing the launch date costs nothing except time in the market.
The seed eligibility works the same way. The $1,000 federal contribution is tied to when your child was born, not when you open the account. A child born in 2027 who has their account opened in 2029 receives the same $1,000 seed as one whose account was opened on day one.
Open the account as soon as you are ready. The only thing lost by waiting is time spent compounding.