One Tax Year, Several CSEDs: Calculating Each Assessment Separately

The collection statute runs from assessment, and the IRS can assess the same tax year more than once. Every time it does, a new ten-year clock starts for the new amount. That is how one year ends up with two, three, or more expiration dates on the same transcript.

The rule behind it

IRC 6502(a) allows collection within 10 years after the assessment of the tax. IRM 5.1.19.1.1 reads that as written: each tax assessment has its own CSED. Not each tax year. Each assessment.

Which transaction codes start their own clock

IRM 5.1.19.2.1 lists transaction codes that carry their own CSED. The ones you will see most often on individual and small business accounts:

When a penalty is assessed on the same day as the tax, both clocks start together and expire together. When a penalty or additional tax is assessed later, it gets a later CSED. IRM 5.1.19.4 adds a reminder that in some instances penalties may have a CSED apart from any other assessment on the module.

How it happens in real cases

• An audit. The original return was assessed in 2021. The exam closes in 2023 and the deficiency is assessed with TC 300. Two CSEDs.
• An underreporter case. A CP2000 for an unreported 1099 becomes a TC 290 assessment years after filing. Another CSED.
• A substitute for return, then your own return. IRM 5.1.19.3.15 says that if the IRS assessed tax under a substitute for return and you later file a return showing more tax, the original CSED stays and a second CSED is established for the increase. If your return shows less tax, the assessment is reduced and the original CSED stays.

Worked example: three assessments, one year

A 2020 Form 1040 shows these assessments on the transcript:

Same tax year. Expiration dates spread across almost four years.

Add a tolling event

Now the taxpayer submits an offer in compromise covering the 2020 year. It is accepted for processing March 1, 2027 and rejected August 30, 2027. No appeal. Under IRC 6331(k)(1) and (k)(3), the statute is suspended while the offer is pending and for 30 days after rejection, through September 29, 2027. That is 212 days.

Suspensions apply to each assessment covered by the event. The dates move together, but they stay separate. For how to count the offer suspension itself, see the offer tolling guide.

What happens when the first one expires

On January 5, 2032 in the example, the original $14,000 assessment (and whatever remains unpaid on it) can no longer be collected. The audit and underreporter assessments can. IRM 5.1.19.5.4.1 tells IRS employees what to do when the CSED has expired for fewer than all assessments in a module: write off the expired assessment amounts (TC 534) so the balance shown is accurate.

Interest follows its tax

Interest is not on the list of codes with their own CSED. IRC 6601(g) says interest on any tax may be assessed and collected at any time during the period within which the tax to which it relates may be collected. So interest on the original $14,000 expires with that assessment, and interest on the audit deficiency lives as long as the deficiency does.

Payments and multiple CSEDs

Which assessment a payment reduces matters a great deal when they expire on different dates. IRM 5.1.19.4 tells collection employees to apply payments to the module with the most imminent CSED first, including levy proceeds, installment payments, and undesignated voluntary payments. From the taxpayer's side, that is often the worst place for voluntary money. The designation rules are in how the IRS applies payments.

How to build your own CSED table

1. Pull account transcripts for every year with a balance.
2. List every assessment line: TC 150, TC 290, TC 300, separately assessed penalties, and their dates.
3. Add ten years to each date.
4. List every tolling event with start and end dates. Merge overlaps. Add the days to every assessment the event covers.
5. Note any TC 550 entries, which set a CSED directly, and any waivers.

The full counting method is in how to calculate a CSED. For the bigger picture, see Statute of Limitations on IRS Collections.

Worked example: a substitute return, then your own return

IRM 5.1.19.3.15 describes two outcomes when a taxpayer files an original return after the IRS has assessed tax under a substitute for return. Put numbers on both. Say the IRS assessed $20,000 for a year on March 1, 2024, after deficiency procedures on a substitute return. The CSED for that assessment is March 1, 2034.

In the first outcome, the taxpayer files a return in 2025 showing $15,000 of tax, and the IRS accepts it. The assessment is abated by $5,000 to match the return. The original CSED of March 1, 2034 stays in place for the remaining $15,000. Nothing restarts.

In the second outcome, the taxpayer's return shows $26,000 of tax. The original $20,000 assessment keeps its March 1, 2034 CSED, and the extra $6,000 is assessed separately, say on September 3, 2025. That $6,000 gets its own CSED of September 3, 2035. One year now has two expiration dates eighteen months apart, and a payment applied to the wrong one can change which dollars expire first.

Worked example: where levy proceeds land

IRM 5.1.19.4 tells collection employees to apply payments, including levy and seizure proceeds and installment payments, to the module with the most imminent CSED first. Take the three-assessment 2020 account from above after the offer suspension: the original assessment expires January 5, 2032, the audit assessment April 18, 2034, and the underreporter assessment September 10, 2035. Suppose a $10,000 bank levy hits in 2031. Under that instruction, the IRS applies it to the original assessment, the one closest to expiring.

From the IRS's point of view, that is rational: it collects the dollars it is about to lose. From the taxpayer's point of view, it means the levy did nothing to reduce the assessments that will still be collectible for years. A voluntary payment, properly designated in writing under Rev. Proc. 2002-26, could have gone to the audit assessment instead. Levies cannot be designated.

Joint returns and separate clocks

On a joint return, both spouses are liable for the assessment, and they normally share its CSED. Events that suspend the statute for only one spouse split that date. IRM 5.1.19.3.1.1 says that when only one spouse files bankruptcy, the CSED must be determined for each spouse separately, and IRM 5.8.10.7 says an offer by one spouse suspends the statute only for that spouse. After a few years, a joint assessment can carry two CSEDs, one per spouse, on top of the separate CSEDs for each assessment. Track them in a grid: one row per assessment, one column per spouse.

The grid takes an hour to build from transcripts and saves far more than that in avoided mistakes. It shows which dollars expire next, which events touched which assessments, and where a voluntary payment does the most good.

If the IRS's records and your grid disagree, the IRS has procedures to review and correct a CSED; IRM 5.1.19.6 covers collection statute review.

The bottom line

A tax year does not expire. Assessments do, one at a time, each ten years after it was made, plus suspensions. If you have had an audit, an underreporter notice, or a substitute return, assume you have more than one date. Map them all before you decide what to pay, offer, or wait out.