You can do so by clicking on your Retirement goal > Settings > Feature (Tax-Coordination) > Edit > Modify Tax Coordination > I no longer want Tax Coordination > Send request to Customer Support, and completing the flow. You will be given the opportunity to leave a note regarding your intentions/questions for the Customer Support team that handles those requests.
Note: Requesting tax-coordination to be disabled does not automatically disable TCP right away. The request is sent to the Customer Support team that processes those requests, who will reach out to you about your request and provide more context as to how the disable and subsequent rebalancing in the remaining accounts could work, as well as information regarding potential tax implications. At this point, you may request to disable tax-coordination with rebalancing turned off in the taxable account to minimize taxable rebalancing in the process. You will need to respond to the Customer Support outreach to complete the process of disabling tax coordination.
Betterment is not responsible for tax consequences, missed market opportunities, or other costs that may arise from disabling Tax Coordination.