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FousMassTaxConnect

Get your MassTaxConnect balances and returns by API

Read the balance and return period due on each account panel, your filed returns and your payments from MassTaxConnect, each with one API call. A workflow checks every client's Summary tab each weekday morning and emails you each account with a balance due.

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Works with your own MassTaxConnect account. Fous is an independent product.

What you can build on MassTaxConnect

  • Get account balances and returns due

    Build this

    Reads each account panel on the Summary tab: the account type, its balance, whether it is due or an overpayment, and the most recent return period due.

    Takes
    Client (optional, for third parties)
    Returns
    Account type, balance, balance due or overpayment, most recent period due

  • List filed returns for an account

    Build this

    Opens View Returns in one account panel and reads each period with its return status and the balance for that period.

    Takes
    Account type, client (optional), earliest period (optional)
    Returns
    Period, return status, balance for the period

  • Check payment status

    Build this

    Opens Manage Payments and Returns under the More... tab and reads the Payments list, pending or processed, with each payment's status.

    Takes
    Pending or processed, client (optional)
    Returns
    Account type, period, amount, payment date, status, confirmation number

  • Save a return for a period as a draft

    Build this

    Opens the period in an account panel, selects File Now, fills in the return and saves it as a draft for a person to review and submit.

    Takes
    Account type, period, return figures, client (optional)
    Returns
    Account type, period, confirmation number, draft status

Automate MassTaxConnect with a workflow

A workflow runs your methods as one process, with nobody at the screen. A schedule or a call from your own system starts it, the steps run in order, and the result arrives in your inbox or in the systems you already use.

  • Balances due on every client's accounts

    Build this
    Starts
    Every weekday at 7:00
    Step 1
    For each client you name, get the account balances and returns due from the Summary tab.
    Step 2
    Keep the accounts with a balance due or a return period due.
    Step 3
    Email you the list, one section per client.

  • Processed payments, posted to your accounting system

    Build this
    Starts
    Every weekday at 8:00
    Step 1
    Check payment status with Processed selected.
    Step 2
    Keep the payments that were not processed on the last run.
    Step 3
    Post each one, with account type, period, amount and confirmation number, to your webhook.

  • Weekly return status for each client

    Build this
    Starts
    Every Monday at 9:00
    Step 1
    For each client and account type you name, list the filed returns.
    Step 2
    Keep the periods whose status or balance changed since the last run.
    Step 3
    Email you a short summary grouped by client.

You can run a workflow by hand on every plan, Free included. Schedules and webhook triggers come with the paid plans, from $29 a month.

Once built, one call from your code

Once you have built a method, it is one POST to /v1/runs from your backend, or a tool an AI agent calls over MCP. This is what “Get account balances and returns due” would look like.

Example request
curl https://api.fous.com/v1/runs \
  -H "Authorization: Bearer $FOUS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "method": "mtc.dor.state.ma.us/get_account_balances",
    "input": {
      "client": "Northwind Cafe LLC"
    }
  }'
Example response
{
  "status": "completed",
  "data": {
    "client": "Northwind Cafe LLC",
    "accounts": [
      {
        "account_type": "Sales and Use Tax",
        "balance": 0,
        "balance_kind": null,
        "most_recent_period_due": "2026-10-31"
      }
    ],
    "count": 1
  }
}

An example with invented data, not a ready-made endpoint. The method exists in your organization once you build it, and its name, inputs and fields follow your request.

MassTaxConnect’s own options

DOR offers bulk filing: returns, reports and payments sent in one transmission as an ASCII or XML file in a predefined layout. You upload files of up to 250 MB in MassTaxConnect; larger files and other file types go through the Bulk File Portal. DOR's pages describe file uploads, not an API that reads your account, and DOR does not create files or provide software.

OptionWhat it coversWhat it takes
Bulk file upload in MassTaxConnectWithholding, pension withholding, 1-ES, 2-ES and 1099-HC files in DOR's layouts. Exceptions arrive as e-messages.A MassTaxConnect login, Submit a bulk file under More..., an ASCII or XML file of 250 MB or less built to DOR's layout.
Bulk File PortalBulk files over 250 MB, or of a type MassTaxConnect does not accept. Confirmation comes as an acknowledgment file to download.Preauthorization through the portal's registration. No file size limit.
MassTaxConnect by handAccount panels, returns by period, payments, letters and e-messages, one taxpayer at a time. A filed return saves as a PDF.A MassTaxConnect logon, and third-party access approved by each client.

Read on November 12, 2026: Bulk Filing FAQs, General information about using MassTaxConnect, Third-party access to MassTaxConnect FAQs.

Signing in to MassTaxConnect

MassTaxConnect signs you in with a username and password and logs you out after 30 minutes of inactivity. A tax preparer uses their own logon, with each client's accounts added once the client approves access. With Fous you sign in once with your own account: the login is sealed with AES-256, never returned by the API, and when a session ends Fous signs back in.

Worth knowing

Your account updates each night
DOR updates accounts nightly with address changes and processed returns and payments. A payment may take several days to process, so read balances in the morning.
A draft also gets a confirmation number
MassTaxConnect gives a confirmation number even for a saved draft. The return is filed only once you select Submit, and only payments with a status of Submitted can be deleted.
Access type decides what a logon can do
A Master Administrator can set a Tax Administrator to View Only, File and Pay or All Access. A View Only logon is enough for methods that only read.
Clients come through third-party access
A Form M-2848 does not give access to a client's accounts. The third party requests access, the client approves it, and the clients then appear on the third party's All tab.

More in Government: US state and local tax

Other industries: MiUI Employer Portal, McMaster-Carr, Upwork, Alliance Healthcare portal (UK), Optum Financial employer portal, Legal Tracker.

Frequently asked questions

Not one that reads your account. DOR offers bulk filing instead: ASCII or XML files in its own layouts, uploaded in MassTaxConnect up to 250 MB, or through the preauthorized Bulk File Portal for larger files. Balances, returns, payments and letters are read on screen.

Yes, with a workflow you build: on a schedule it loops over the clients on your All tab, reads each client's account panels and emails you the balances in one list. In MassTaxConnect itself, each client's balances are on that client's own account panels.

Open Manage Payments and Returns under the More... tab and show Payments: Pending lists those not yet processed, Processed the rest. Your balance reflects a payment once it is processed, which may take several days.

11:59 p.m. on the due date, to avoid penalty and interest. If the due date falls on a weekend or holiday, the payment is due the following business day.

No. Fous is an independent product. You use it with your own MassTaxConnect logon, and a method reads and does only what that logon's access allows.

Put MassTaxConnect behind an API call

Describe one job in Studio and see the method it builds, with 100 credits a month and no credit card, or book a demo and bring the sites your team signs in to.

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Read nextMichigan Treasury OnlineMinnesota e-ServicesMy DORMiUI Employer PortalHow methods workHow workflows run

Fous is an independent product: it is not affiliated with, endorsed by or sponsored by the operator of MassTaxConnect (Massachusetts Department of Revenue). The name is used only to say which system this page is about. Something here wrong or out of date? Write to legal@fous.com.