To add an existing 529 account to Betterment, first log into your Betterment account from a web browser. From here, click Add New on the left hand side of the page to add a new goal and select 529s. Next, select Connect an existing 529. Here you will have the option to select your 529 Plan.
If your plan is not listed then it is a plan that Betterment does not integrate with directly. Click the Don’t see your 529 Plan? button to continue to connect your 529 as an external account via Plaid. Please note, connecting an external account will limit employer-sponsored benefits like making payroll contributions or receiving an employer match.