2025-06-30
The Tax Court assigns docket numbers to cases before the court. For example, the docket number for the recent case of AbbVie, Inc. v. Commr., 164 T.C. No. 10, is:
2597-23
The last two digits are the year the petition was filed, and the numbers before the dash are incremental numbers assigned as the petitions come in. Some docket numbers have letter suffixes.
The recent case of Smith v. Commr., T.C. Summary Opinion 2025-6, has a docket number of:
372-23S
The "S" suffix indicates that the case was heard pursuant to the ["small"] provisions of Code §7463 (disputes involving $50,000 or less).[1] The Tax Court website has over 3,000 opinions with docket numbers having an "S" suffix, with the first of these opinions being published in 2001.[2]
The "L" suffix indicates the opinion deals with the review of a collection due process ("CDP") hearing under Code §6320. The Tax Court website has over 2,000 opinions with docket numbers having an "L" suffix, with the first of these opinions being published in 2000.[3]
Some opinions deal with small cases and CDP hearings. The docket numbers for these have a suffix of "SL". There are less than 200 of these opinions on the Tax Court website.
The "W" suffix is for whistleblower claims filed under Code §7623. The Tax Court website has fewer than 100 opinions with docket numbers having a "W" suffix, with the first of these opinions being published in 2010.[4]
The "X" suffix is for tax exempt organizations under Code §501(c)(3). The Tax Court website has fewer than 60 opinions with docket numbers having an "X" suffix.
The "R" suffix is for retirement plans. The Tax Court website has fewer than 30 opinions with docket numbers having an "R" suffix.
The "P" suffix is for IRS certifications of seriously delinquent tax debts to the Secretary of State for action with respect to denials of passports under Code §7345. The Tax Court website has 13 opinions with docket numbers having a "P" suffix, with the first of these opinions being published in 2020.[5]
There are only two opinions on the Tax Court website with docket numbers having a "D" suffix:
Both of these opinions deal with public disclosure of written determinations (e.g., PLRs) under Code §6110.
It would seem that the Tax Court may be inadvertently revealing the name of the taxpayer in the first of the two anonymous opinions (docket number (28246-07D). If you go to https://dawson.ustaxcourt.gov/, click on the "opinion" tab, and paste 28246-07D into the docket number field, the case title is:
Millennium Multiple Employer Welfare Benefit Plan and Millennium Marketing Group
If you click through to see the opinion itself, it comes up as Anonymous v. Commr. I presume that the case title is the name of the "anonymous" taxpayer.
Below are percentages of all opinions by type and by docket suffix for opinions published from 1996 to 2024.
There is no official published guide as to the meanings of the suffixes. The descriptions in this blog post are based on a review of the opinions containing the suffixes. Docket suffixes S and L are briefly mentioned in IRM 35.3.23.3, and docket suffixes are also mentioned on page 3 of the Tax Court DAWSON Public Guide. ↑
The earliest summary opinion published on the Tax Court website is Shapiro v. Commr., T.C. Summary Opinion 2001-4. Summary Opinions 2001-1 through 3 were published by the Tax Court, but are not included on its website. ↑
Moore v. Commr., 114 T.C. 171 (2000). ↑
Cooper v. Commr., 135 T.C. 70 (2010). ↑
Ruesch v. Commr., 154 T.C. 289 (2020). ↑