CLIENT RESOURCE CENTER

Client Portal

Information about using the client portal, how-to videos, and scheduling for personalized assistance.

Instructions & links for tax due, extension payments, and estimated tax payments.

Visit our tax blog for articles about the latest in tax related news.

Previous year tax returns completed by Seaport Tax are always available in the client portal within the Docs section.
We can also send copies of previous tax returns to you or third parties with your permission.
Requests can be sent to Clients@seaportpartners.com
You can email questions directly to your tax team or to the Client Relationship Associate at Clients@seaportpartners.com, who will direct your message to the correct team members.
You can monitor the status of your returns within your portal, where you are able to see updates as they happen.
You will be able to see if additional documents are needed from you, or when it is being prepared to send to you.
You can schedule a meeting with your team by reaching out to the Client Relationship Associate at Clients@seaportpartners.com, who will be happy to coordinate.
If your engagement with Seaport includes touchpoints throughout the year, your tax team will reach out to you as the time approaches.
Paper tax documents can be mailed to our secure P.O. box:
Seaport Tax LLC
405 Waltham St, Suite 357
Lexington, MA 02421
Once your documents have been scanned, they will be mailed back to you for your records.
Checks can be mailed directly to our Boston office:
Seaport Tax
175 Portland St, Fl 4
Boston, MA 02114
If you have additional questions, not addressed here, you can email Clients@seaportpartners.com‍ and a member of the admin team will be able to help you.

Business Tax Documents Due

February 23, 2026
For the timely filing of business returns due March 16th, please upload or mail all tax documents by February 23rd.
If documents are sent after this date, we cannot guarantee filing by the tax deadline and an extension may be required.
Business Tax Return Deadline

March 16, 2026
Partnership and S-Corp tax returns must be e-filed or extended by this date.
Tax Documents Due

March 25, 2026
For the timely filing of returns due April 15th, please upload or mail all tax documents by March 25th.
If documents are sent after this date, we cannot guarantee filing by the tax deadline and an extension may be required.