SEAPORT TAX CLIENTS

INFORMATION & LINKS

Client Portal

Information about using the client portal, as well as our library of how-to videos and a scheduling link for one-to-one assistance.  

Client portal

Tax Payments

Instructions & links for making 2025 tax due payments, 2025 extension payments, and 2026 estimated tax payments.

tax payments

Seaport Tax Blog

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

seaport blog

FREQUENTLY ASKED QUESTIONS

  • 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

  • Your tax team and their contact information is now available to view in your client portal. Using the top menu, you can navigate to:

    Docs > Engagement Docs > Tax Team

    You can also email Clients@seaportpartners.com and the document can be emailed to you.

  • 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.

  • We include a list in your client portal of all the tax documents need to complete your returns. [WHERE IS IT] This list will also be sent to you in the form of a checklist within the portal, called a client request.

    You will be notified when a client request list is sent to you in the portal and you can check off items as they are uploaded. These lists can also be sent to clients directly via email.

  • 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.

UPCOMING DEADLINES

  • Q4 Estimated Tax Payments

    January 15, 2026

    If you pay estimated tax payments throughout the year, the final estimates for Q4 are due on January 15th. If this applies to your tax situation, you will receive communications ahead of the deadline.

  • Business Tax Documents Due

    February 24, 2026

    For the timely filing of business returns due on March 17th, we ask that all tax documents be uploaded to the client portal or mailed by February 24th.  If documents are sent after this date, we cannot guarantee filing by the tax deadlines and an extension may be required.

  • Business Tax Return Deadline

    March 17, 2026

    Partnership and S-Corp tax returns must be e-filed or extended by March 17th.

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  • It all begins with an idea. Maybe you want to launch a business. Maybe you want to turn a hobby into something more.

  • It all begins with an idea. Maybe you want to launch a business. Maybe you want to turn a hobby into something more.

  • It all begins with an idea. Maybe you want to launch a business. Maybe you want to turn a hobby into something more.