IRS Notice Guide

LT16 Letter: What This IRS Collection Letter Means

By Ray Neu, Publisher | Last reviewed: October 26, 2026 | Reading time: 8 min

Short answer

An LT16 is a letter from the IRS Automated Collection System (ACS) saying the IRS is trying to collect unpaid tax, is missing tax returns, or both. The IRS LT16 page asks for missing returns and payment or a payment plan, and warns of levies and a federal tax lien. It is not the LT11 levy hearing notice.

This guide reads the IRS page for the LT16 next to the Internal Revenue Manual (IRM) chapters that tell ACS staff when the letter goes out and what happens after it. The IRM is internal guidance that the IRS publishes on irs.gov. Where it and the public page read differently, both are shown.

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What the LT16 says

The IRS page explains that the letter arrives because “we’re trying to collect unpaid taxes from you and/or our files show we’re missing tax returns from you.” One LT16 can therefore be about a balance, about unfiled years, or about both at once.

The manual gives the letter two names. IRM 5.19.1.3.2.1 calls it “Please Call Us About Your Overdue Taxes Or Tax Return.” The ACS letter table in IRM Exhibit 5.19.5-2 lists it as “You Have Unpaid Taxes or Unfiled Returns.” That table also says ACS letters are issued to the taxpayer and to authorized representatives, and that the back of each letter lists every delinquency by period, form type, assessed balance, statutory additions and total due.

Where ACS fits

IRM 5.19.5.1 says the ACS program was built to give taxpayers or their representatives a way to resolve delinquent accounts “with a single telephone contact.” IRM 5.19.5.1.1 describes ACS as a computerized inventory, set up in April 1984, that holds both balance due accounts and return delinquency investigations. The LT16 page likewise sends several kinds of questions to the toll-free number on the notice.

Why the IRS sends an LT16

The public page gives the reason in a single sentence. The manual shows the account conditions under which ACS employees or the system send the letter. Two examples:

No levy source found. Under IRM 5.19.5.6.1.1, when phone attempts fail and there is “no productive levy source,” the employee moves the case to the I4 investigation unit “and issue LT16.”
A defaulted payment plan. IRM 5.19.5.4.2 says certain defaulted installment agreements go through routine new case analysis and “may have an LT16 issued.”

The manual handles the LT11 differently. IRM 5.19.4.3.1 tells employees to issue an LT11 “ONLY where the next action will be to levy,” and says “If there is no levy source available, do not issue LT11.” In the cases these sections describe, the LT16 goes out where ACS has no levy source to act on, while the LT11 is kept for when a levy is the next step.

What the letter asks for

The LT16 page sets no number of days for a reply. Its steps, in order:

Read the notice. It identifies “which tax returns are missing from IRS records,” which may cover several years. The page adds that following the notice’s instructions “may stop enforcement action.”
File the missing returns “as soon as possible,” if the notice lists any.
Pay, or arrange a plan. The page says interest and penalties stop being added once the balance is paid in full. A taxpayer who cannot pay everything is told to pay what is possible and set up an installment agreement, which requires being “current on your filings.” Balances under $50,000 are pointed to the Online Payment Agreement application. The installment agreement guide covers the plan types.
Raise a hardship. The IRS can report an account currently not collectible and delay collection. The page says this status does not stop penalties and interest, and that the caller should be ready to discuss income, expenses and assets, with proof possibly requested.
Disagree. A taxpayer who disputes the tax or cannot settle a disagreement is, in the page’s words, “entitled to a hearing with the Office of Appeals,” with Publication 1660 as the reference.

Already filed or already paid

Payments can take up to 21 days to post. If the balance was paid in full within the last 21 days, the page says to disregard the LT16.
For a return mailed more than 10 weeks ago, the page asks for a signed copy to be sent again. A return reported as missing by mistake is handled by calling the number on the notice.
Someone who believes no return was required can check the IRS “Do I need to file a tax return?” tool, then call if the notice still shows a return as due.
An approved installment agreement stays in place: the page says to keep making the agreed payments.

Questions about an LT16?

An attorney can review the tax years and balances the letter lists and the filing and payment routes the IRS describes.

Start Your Free Evaluation Call (202) 968-1121

What can follow an LT16

According to the LT16 page, enforcement “can include seizing your assets or wages,” and could also mean a notice of federal tax lien, which “could affect your credit score and ability to borrow.” The IRS enforced collection page it links says that when taxes go unpaid and the IRS is not told why, “the law requires that enforcement action be taken.” Its list includes a notice of levy on salary, bank accounts or property, and a summons to the taxpayer or third parties “to secure information to prepare unfiled tax returns or determine the taxpayer’s ability to pay.”

Possible assignment to a revenue officer

IRM 5.19.5.4.11.5 describes I4, the unit where LT16 cases without a levy source are placed, as “final attempts” to locate the taxpayer or assets before the account is reported currently not collectible, sent on a “transfer to field,” or transferred to the queue. IRM 5.19.5.8.4.1 ties field transfers to revenue officer assignment. Publication 594 says collection “could include a visit from a Revenue Officer,” and that before a visit the officer normally “mails an appointment letter or calls.” The I4 description lists the field alongside currently not collectible status and the queue, so a revenue officer is one possible outcome rather than the only one.

The unfiled return side and the balance side

Missing returns

The manual treats the LT16 as a return delinquency letter as well. IRM 5.19.2.8.1 says that once an LT16 has gone to the current address, a separate LT26 (“Please File Your Tax Return Immediately”) is not needed. If returns stay unfiled, Publication 594 says the IRS may file a substitute return that “might not give you credit for deductions and exemptions.” The IRS past due returns page says Notice CP3219N then proposes an assessment, with 90 days to file the return or petition the Tax Court.

Refunds are affected too. The IRS holds income tax refunds while its records show returns past due, and the LT16 page says a refund on a late return requires filing within three years of the original due date, or within two years of full payment, if applicable. The unfiled tax returns guide covers the filing side in more depth.

The balance

The LT16 page says interest generally accrues daily from the return due date, and that interest and penalties keep accruing until the balance is paid in full, even under a pending or approved installment agreement. It also mentions an offer in compromise, which in some circumstances settles a tax debt for less than the full amount. The back taxes guide sets out how balances, penalties and payment options work.

How the LT16 compares with the LT11

IRM 5.19.4.3.4 says that if an LT16 gets no response by the follow-up date, employees “proceed with the levy determination.” A levy generally needs a further notice first: IRM 5.19.4.3.1 says § 6330 requires a Collection Due Process notice at least 30 days before a levy, with exceptions that include jeopardy levies and state income tax refund levies. In ACS that notice is the LT11; when a revenue officer handles the case, it is Letter 1058.

Point	LT16	LT11
Title in IRM Exhibit 5.19.5-2	You Have Unpaid Taxes or Unfiled Returns	Final Notice, notice of intent to levy and right to a hearing
Mailing noted in the table	Not stated	Certified, return receipt requested
When the IRM uses it	For example, no productive levy source, or a defaulted plan	Only where the next action will be to levy

What the hearing notice means and the deadline it carries are covered in the LT11 and Letter 1058 guide.

When an attorney matters

The LT16 page says “You don’t need to seek assistance to contact us,” and that getting outside help “will not result in the IRS giving preferential treatment.” Publication 594 says that during collection a taxpayer may act alone or be represented by an attorney, a certified public accountant, an enrolled agent, an immediate family member, or anyone enrolled to practice before the IRS, with Form 2848 used for a representative to appear, contact the IRS or receive confidential material. The roles differ in a few places:

Privilege. Under § 7525, the attorney-client style confidentiality that covers federally authorized tax practitioners, such as CPAs and enrolled agents, can be asserted only in noncriminal tax matters. The IRS past due returns page says repeated failure to file can bring “additional penalties and/or criminal prosecution.”
Copies and access. The ACS letter table says LT letters are issued to authorized representatives as well as the taxpayer. The IRS Form 2848 page says authorizing a representative also lets that person receive and inspect confidential tax information.

The attorney vs CPA vs enrolled agent comparison covers the roles in more depth.

Related guides

Frequently Asked Questions

Is an LT16 a notice of intent to levy?

Not according to the IRM letter table, which titles the LT16 “You Have Unpaid Taxes or Unfiled Returns” and lists the LT11 as the final notice of intent to levy with hearing rights. The LT16 page still warns that enforcement can include seizing assets or wages and filing a notice of federal tax lien.

What if I already filed the return the LT16 says is missing?

The IRS page says that if more than 10 weeks have passed since the return was sent, a signed copy should be sent again. If a return was reported as missing in error, the page directs taxpayers to the toll-free number on the notice.

Can I disregard an LT16 if I just paid?

The IRS page says payments can take up to 21 days to post, and that if the balance was paid in full within the last 21 days, the LT16 can be disregarded.

Can an LT16 lead to a revenue officer?

It can be one step on that path. The IRM places LT16 cases without a levy source in a unit making final attempts before currently not collectible status, transfer to field, or transfer to the queue. Publication 594 says collection can include a revenue officer visit, normally arranged by letter or phone first.

Can I get a payment plan after an LT16?

The LT16 page says an installment agreement can cover the remaining balance for a taxpayer who is current on filings, and points balances under $50,000 to the Online Payment Agreement application.

Talk through an LT16

A free, confidential evaluation can help sort out the filing and payment questions the letter raises.

Start Your Free Evaluation Call (202) 968-1121

About the Author

Ray Neu

Ray Neu is the publisher of IRSAttorneys.net. A former law enforcement officer with a background in criminal justice and digital publishing, he oversees editorial direction, partnership standards, and compliance review for the site. He is not an attorney and does not provide legal advice; all tax law content is sourced and reviewed against the standards documented on the Editorial Team & Standards page.

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Results described on this website are not a guarantee, warranty, or prediction of the outcome of any tax matter. Every situation is different. Prior results do not guarantee a similar outcome. Article content reflects general information about federal tax procedure as of the last reviewed date and may not reflect subsequent changes in IRS policy, regulations, or case law.