# Get your MyTax Illinois returns and letters through an API

> Read your submitted returns, IDOR letters and account period balances from MyTax Illinois with one API call each. A workflow can check View Letters every weekday morning and email you each new letter with its Letter ID and tax account.

Page: https://fous.com/automate/mytax-illinois
Updated: 2026-11-12

Works with your own MyTax Illinois account. Fous is an independent product.

## What you can build on MyTax Illinois

### Get submitted returns

Reads Manage Payments and Returns with Show set to Returns: each return filed for a tax account, its period, status and confirmation number.

- Takes: Tax account, period (optional)
- Returns: Return type, tax account, period, submitted date, status, confirmation number

### List IDOR letters

Reads the Letters tab under More, then View Letters: the copies of correspondence IDOR mailed to you, with each letter's Letter ID and date.

- Takes: Mailed since (optional)
- Returns: Letter ID, letter name, tax account, period, date mailed

### Get account periods and balances

Opens View more account options for one tax account, then View Account Periods under Periods and Submissions, and reads each period with its balance.

- Takes: Tax account
- Returns: Tax account, period end date, balance

### Pay a period by bank account debit

Opens a period in View Account Periods, selects Make a Payment and Bank Account Debit, enters the amount and date and submits the payment.

- Takes: Tax account, period end date, payment type, amount, payment date
- Returns: Confirmation number, tax account, period, amount, payment date, status

## Automate MyTax Illinois with a workflow

A [workflow](/product/workflows) 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.

### New IDOR letters, every weekday

Starts: Every weekday at 8:00 Central time

1. List the letters on the Letters tab under View Letters.
2. Keep the letters that were not there on the last run.
3. Email you each new letter's Letter ID, name, tax account, period and date mailed.

### Returns still Pending after a day

Starts: Every weekday at 9:00 Central time

1. For each tax account you name, get the submitted returns.
2. Keep the returns still Pending that were submitted before today.
3. Post tax account, return type, period, submitted date and confirmation number to your webhook.

### Monthly balance check across tax accounts

Starts: Monthly on the 1st at 7:00 Central time

1. For each tax account you name, get the account periods and their balances.
2. Keep the periods with a balance other than zero.
3. Email you one list grouped by tax account, with period end date and balance.

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](/product/methods), it is one POST to /v1/runs from your backend, or a tool an AI agent calls over MCP. This is what “Get submitted returns” 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": "mytax.illinois.gov/get_submitted_returns",
    "input": {
      "tax_account": "Sales & Use Tax",
      "period": "2026-10"
    }
  }'
```

Example response:

```
{
  "status": "completed",
  "data": {
    "tax_account": "Sales & Use Tax",
    "returns": [
      {
        "return_type": "ST-1",
        "tax_account": "Sales & Use Tax",
        "period": "2026-10",
        "submitted_date": "2026-11-11",
        "status": "Pending",
        "confirmation_number": "0-482-913-570"
      }
    ]
  }
}
```

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.

## MyTax Illinois’s own options

IDOR describes electronic filing programs for software, not an API for reading a MyTax Illinois account. ST-1 and ST-2 returns can be sent from your own or approved software, and withholding returns through FSET, both after enrollment on MyDevPortal and testing. Letters, balances and submissions are read in MyTax Illinois, which is free.

| Option | What it covers | What it takes |
| --- | --- | --- |
| Sales and use tax electronic filing | Forms ST-1 and ST-2 sent from your own software or from an approved third-party software vendor. | The Business Electronic Filing Enrollment Application on MyDevPortal, then testing with IDOR. Build to implementation guide STS-81. |
| FSET for withholding | IL-941 and IL-941-X returns and payments for large employers and payroll companies. | Enrollment on MyDevPortal, a Letter of Intent, then testing. Reporting agents need Form IL-8655 from each client. |
| Submit Bulk W2/1099 File | W-2 and 1099 forms filed in bulk from the MyTax Illinois home page, without a logon. | A bulk W-2 or 1099 file, submitted from the Non-Login Return or Report panel. |
| MyTax Illinois by hand | Filing returns, making payments, reading letters and viewing account periods. | A free MyTax Illinois logon for a registered business. |

Read on November 12, 2026: [Sales and use tax electronic filing](https://tax.illinois.gov/taxprofessionals/electronicfiling/sales.html), [Withholding and unemployment insurance (FSET)](https://tax.illinois.gov/taxprofessionals/electronicfiling/withholding.html), [MyTax Illinois functions](https://tax.illinois.gov/programs/mytax/help/mytax-illinois-functions.html).

## Signing in to MyTax Illinois

MyTax Illinois signs you in with a username and password, or a passkey, then a two-step verification code sent by email, text message or an authenticator app. You choose a primary and a backup method, and a trusted browser can skip the code. With Fous you sign in once through MyTax Illinois's own sign-in: the login is sealed with AES-256, emailed codes are handled and an expired session is signed back in.

## Worth knowing

- **Requests are processed once a day**: A submitted return or payment shows Pending until IDOR processes it, usually once a day, then Completed. A balance can take up to five business days to update after a payment.
- **Only a pending payment can be cancelled**: A return can be withdrawn from Submissions, then edited or deleted. A payment cannot be edited, and it can be cancelled only while its status is pending.
- **Business income tax returns are filed elsewhere**: Business income tax returns cannot be filed or amended in MyTax Illinois. You can still pay a period there, through View Account Periods and Make a Payment.
- **The Master logon controls other users**: The Master logon holder decides whether additional logons are allowed and creates them. Third-party access is granted under Manage third party access, and is not available for accounts administered by IDES.

## More in Government: US state and local tax

- [Ohio Business Gateway](https://fous.com/automate/ohio-business-gateway.md)
- [MyFTB](https://fous.com/automate/myftb.md)
- [CDTFA Online Services](https://fous.com/automate/cdtfa-online-services.md)
- [Colorado Revenue Online](https://fous.com/automate/colorado-revenue-online.md)
- [Florida DOR eServices File and Pay](https://fous.com/automate/florida-dor-eservices-file-and-pay.md)
- [Georgia Tax Center](https://fous.com/automate/georgia-tax-center.md)
- [INTIME](https://fous.com/automate/intime.md)
- [LaTAP](https://fous.com/automate/latap.md)
- [Maryland Tax Connect](https://fous.com/automate/maryland-tax-connect.md)
- [MassTaxConnect](https://fous.com/automate/masstaxconnect.md)
- [Michigan Treasury Online](https://fous.com/automate/michigan-treasury-online.md)
- [Minnesota e-Services](https://fous.com/automate/minnesota-e-services.md)
- [My DOR](https://fous.com/automate/my-dor.md)
- [myconneCT](https://fous.com/automate/myconnect.md)
- [MyDORWAY](https://fous.com/automate/mydorway.md)
- [myPATH](https://fous.com/automate/mypath.md)
- [MyTaxes Kentucky](https://fous.com/automate/mytaxes-kentucky.md)
- [NCDOR eBusiness Center](https://fous.com/automate/ncdor-ebusiness-center.md)
- [New Jersey Tax Portal](https://fous.com/automate/new-jersey-tax-portal.md)
- [NY Business Online Services](https://fous.com/automate/ny-business-online-services.md)
- [OH|TAX eServices](https://fous.com/automate/oh-tax-eservices.md)
- [Texas Comptroller Webfile](https://fous.com/automate/texas-comptroller-webfile.md)
- [TNTAP](https://fous.com/automate/tntap.md)
- [Virginia Tax Business Online Services](https://fous.com/automate/virginia-tax-business-online-services.md)
- [Wisconsin My Tax Account](https://fous.com/automate/wisconsin-my-tax-account.md)

Other industries: [bizfile Online](/automate/bizfile-online), [モノタロウ](/automate/monotaro), [e-staffing](/automate/e-staffing), [NHSBSA Manage Your Service](/automate/nhsbsa-manage-your-service), [The Hartford EBC](/automate/the-hartford-ebc), [Money Claim Online](/automate/money-claim-online).

## Frequently asked questions

### Does MyTax Illinois have an API?

Not for reading an account. IDOR runs electronic filing programs for software: ST-1 and ST-2 through the sales and use tax program, and IL-941 through FSET, both after enrolling on MyDevPortal and testing. Letters, balances and submissions are read in MyTax Illinois itself.

### Can my accountant or payroll provider use our MyTax Illinois account?

Yes, through third-party access or an additional logon. Third-party access is granted under Manage third party access, and the Master logon holder creates additional logons. Third-party access is not available for accounts administered by IDES.

### Where do I find letters IDOR mailed to me?

Under More, then View Letters. The Letters tab holds copies of correspondence IDOR mailed to you, each with its own Letter ID. Messages are separate one-way notices you cannot reply to.

### Can I file ST-1 returns from my own software?

Yes, after enrolling and testing. You complete the Business Electronic Filing Enrollment Application on MyDevPortal and build to STS-81, which describes ST-1 version ST1V6.0 for January 2026 periods and later. You can also buy software from an approved vendor.

### Is Fous affiliated with the Illinois Department of Revenue?

No. Fous is an independent product. You use it with your own MyTax Illinois logon, and a method reads and does only what that logon can.

Fous is an independent product: it is not affiliated with, endorsed by or sponsored by the operator of MyTax Illinois (Illinois 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.