Which IRS Letters Are Sent by the Automated Collection System (ACS)?

When you owe the IRS and ignore their letters, they won’t just go away. In fact, the notices will keep coming, and they’ll get more serious over time. Many of these letters aren’t sent by a person but are automatically generated by the IRS’s Automated Collection System, or ACS. So if you’re receiving letters about unpaid taxes and wondering who’s sending them, it’s likely the ACS behind it.

In this post, we’ll break down the most common IRS letters sent by ACS, what each one means, and what actions they can lead to if ignored.

What Is the IRS ACS?

The IRS Automated Collection System is a computerized program designed to collect unpaid taxes from taxpayers who haven’t responded to earlier notices. Unlike cases assigned to human Revenue Officers, ACS cases are handled entirely through call centers and automated notices…or at least at the start.

If your case is with ACS, you’ll typically receive a series of escalating letters before the IRS takes enforced collection actions like levies or garnishments.

Common IRS Letters Sent by ACS

Here are the main notices you might receive if your tax debt is being handled by ACS:

1. CP14 – Balance Due Notice

The CP14 notice is typically the first letter the IRS sends when you owe taxes. It outlines the amount you owe, including any penalties and interest, and explains how to pay. Although this letter carries a relatively low risk if addressed promptly, ignoring it will lead to further notices.

2. CP501 – First Reminder Notice

If no action is taken after the CP14, the IRS follows up with the CP501. This is a reminder that the balance remains unpaid and encourages you to pay or get in touch with the IRS. The tone of this letter is slightly more urgent, signaling the start of the escalation process.

3. CP503 – Second Reminder Notice

The CP503 comes next, usually within a few weeks of the CP501. This notice has stronger language, warning that the IRS still hasn’t received payment and that more serious collection actions may be coming soon.

4. CP504 – Final Notice Before Levy

The CP504 is one of the most serious letters sent by ACS. It serves as a final warning that the IRS intends to levy certain property, such as your state tax refund, if the debt remains unpaid. This is not a notice of actual seizure yet, but it’s the IRS making clear they’re prepared to take action. At this point, immediate action is strongly recommended.

5. LT11 or Letter 1058 – Final Notice of Intent to Levy and Your Right to a Hearing

The LT11 (or its legal twin, Letter 1058) is the most serious notice in the ACS collection process. It informs you that the IRS intends to levy your property, including wages or bank accounts, and gives you the right to request a Collection Due Process (CDP) hearing within 30 days. While this letter can be sent by a Revenue Officer if your case is assigned to one, many of these notices come from ACS.

• Action required: File Form 12153 if you want to stop the levy and request a hearing.

6. CP90 / CP91 – Final Notice Before Levy on Social Security Benefits

These are specialized levy notices targeting taxpayers who receive Social Security income. CP90 or CP91 warns that the IRS intends to begin garnishing a portion of your benefits if no payment or resolution is arranged. Like the LT11, these notices also give you the right to request a hearing.

7. CP521 – Installment Agreement Reminder

If you’ve already entered into a payment plan with the IRS, the CP521 is a monthly reminder of your upcoming due date. It helps keep your agreement on track by reminding you to submit timely payments.

8. CP523 – Notice of Defaulted Installment Agreement

If you miss payments or otherwise fail to comply with your agreement, the IRS will send a CP523 notice informing you that your installment agreement is in default. It also warns that the IRS may terminate the agreement and resume enforced collection actions such as levies or liens. Fortunately, you may still have time to reinstate your plan before more aggressive steps are taken.

Final Thoughts

If you’ve received any of the letters listed above, particularly a CP504 or LT11, now is the time to act. These notices are not just paper; they’re legal warnings that the IRS is gearing up to take your assets. Working with a tax professional can help you stop a levy, set up or reinstate an installment agreement, or explore other resolution options like an Offer in Compromise or Currently Not Collectible status.

Don’t wait until it’s too late. If you’re facing IRS collection letters, especially those from ACS, take action today. The sooner you respond, the more options you’ll have, and the better your chances of protecting your income and assets. Let’s talk. Call now for your free, confidential consultation and take the first step toward resolving your tax issues.