opinion: Thomas A. JOHNSON, Plaintiff-Appellant, v. UNITED STATES of America, Defendant-Appellee.
  No. 843, Docket 92-6231.
  United States Court of Appeals, Second Circuit.
  Submitted Feb. 25, 1993.
  Decided March 31, 1993.
  Thomas A. Johnson, pro se.
  James A. Bruton, Acting Asst. Atty. Gen., Dept, of Justice, Tax Div., Washington, DC (Gary R. Allen, William S. Esta-brook, Billie L. Crowe, Philip H. Karter, Attys., Dept, of Justice, Tax Div., Washington, DC, Albert S. Dabrowski, U.S. Atty. for D. Conn., New Haven, CT, H. Gordon Hall, Asst. U.S. Atty., of counsel), for defendant-appellee.
  Before: LUMBARD, McLAUGHLIN, Circuit Judges, and DUFFY, District Judge.
  Hon. Kevin Thomas Duffy, United States District Judge for the Southern District of New York, sitting by designation.
  LUMBARD, Circuit Judge:
  Thomas A. Johnson, pro se, appeals from an order of the District Court of Connecticut, Dorsey, J, granting the government’s motion for summary judgment in his action to quiet title to his property by removing a tax lien. Johnson contends that this ruling was in error because the IRS assessed the tax which formed the basis of the lien before his time for filing an appeal expired. We agree and reverse.
  On August 2, 1990, the Tax Court, Wright, /., determined that Johnson was liable for income tax deficiencies for the taxable years 1980 through 1984. On September 24, 1990, 53 days after this ruling, the IRS assessed Johnson for these deficiencies, and on July 9, 1991, the IRS filed a tax lien on Johnson’s real and personal property in the amount of $347,364.33.
  Johnson brought this suit, pursuant to 28 U.S.C. § 2410(a) (1988), to quiet title to his property, claiming that the lien was invalid because the IRS assessed the deficiency prior to the Tax Court’s decision becoming final, in violation of 26 U.S.C. § 6213(a) (1988). Thereafter, the IRS reassessed Johnson’s tax deficiency for 1984, but not for 1980 to 1983 because the statute of limitations for supplemental, assessments had expired.
  Both parties moved for summary judgment on the issue of the validity of an assessment made before expiration of the 90-day period for filing an appeal provided in 26 U.S.C. § 6213(a). By order dated August 17, 1992, Judge Dorsey upheld the assessment, concluding that a tax assessment cannot be stayed during the appeal period unless the taxpayer files a notice of appeal and an appellate bond as provided by 26 U.S.C. § 7485 (1988). Because an assessment made during the unexpired appeal period is void, we reverse.
  A. Jurisdiction
  Initially, we find that the district court had subject matter jurisdiction over this case because 28 U.S.C. § 2410(a) waives the sovereign immunity of the United States. Section 2410(a) states that the United States may be named as a party in “any civil action ... to quiet title to ... real or personal property on which the United States has or claims a mortgage or other lien.” When a federal tax lien is involved, however, an action pursuant to § 2410(a) will not lie if its sole purpose is to challenge the validity of the underlying assessment. See Falik v. United States, 343 F.2d 38, 41 (2d Cir.1965).
  An exception to this restriction permits a party to challenge procedural irregularities in the assessment process by way of § 2410(a). In Kulawy v. United States, 917 F.2d 729, 733 (2d Cir.1990), we held that § 2410(a) permitted the taxpayer to “challenge procedural irregularities in the seizure and sale of his property following such an assessment.” As the Tenth Circuit explained, the scope of this exception includes “procedural violations arising from assessment, levy, and seizure.” Guthrie v. Sawyer, 970 F.2d 733, 735 (10th Cir.1992).
  Because Johnson’s claim is procedural in nature, it falls within this exception. A procedural claim is one which does not challenge “the existence or extent of substantive tax liability.” Guthrie, 970 F.2d at 736. Applying this standard, the Guthrie court held that the alleged failure of the IRS to assess the tax properly or to send valid notices of assessment were procedural defects cognizable in a quiet title suit. Id. at 737. See also Elias v. Connett, 908 F.2d 521, 527 (9th Cir.1990) (failure to send valid notice of assessment is procedural); Brewer v. United States, 764 F.Supp. 309, 314 (S.D.N.Y.1991) (§ 2410(a) may be used to challenge the procedures used in making the assessment). Here, Johnson’s claim is procedural because he disputes the timing of the assessment, not its amount.
  B. Validity of the Assessment
  We find that the assessment was invalid because it was made before the Tax Court’s decision became final. Section 6213(a) provides that “no assessment of a deficiency ... shall be made ... until the decision of the Tax Court has become final.” 26 U.S.C. § 6213(a). A decision becomes final upon expiration of the 90-day period allowed for filing a notice of appeal. See 26 U.S.C. § 7481(a)(1) (1988). In this case, the tax was assessed 53 days after the Tax Court’s decision, well before the period for filing a notice of appeal expired.
  In concluding that the assessment was valid, the district court relied on 26 U.S.C. § 7485, which provides:
  Notwithstanding any provision of law imposing restrictions on the assessment and collection of deficiencies, the review under section 7483 shall not operate as a stay of assessment or collection ... unless a notice of appeal in respect of such portion is duly filed ... and then only if the taxpayer ... has filed with the Tax Court a bond....
  The court interpreted this provision as requiring a taxpayer to file a notice of appeal and to post a bond before an assessment would be stayed.
  As the government now concedes, this reliance is misplaced. Thus, we conclude that the assessment is void because it was made during the unexpired period for filing a notice of appeal. Section 7485 establishes the circumstances under which appellate review of a Tax Court decision stays an assessment. In seeking such review, the taxpayer must file a timely notice of appeal. See 26 U.S.C. § 7483 (1988). Since Johnson did not file a notice of appeal, there is no appellate review, and § 7485 does not apply.
  We also reject the government’s argument that the assessment becomes valid upon the expiration of the appeal period. The assessment violated § 6213(a), and we decline to “give the Commissioner an arbitrary power which it was not intended he should have,” United States v. Yellow Cab Co., 90 F.2d 699, 701 (7th Cir.1937), by validating the assessment. This view is consistent with United States v. Walker, 217 F.Supp. 888, 892 (W.D.S.C.1963), in which the court held an identical assessment, i.e. one made within the appeal period, “null, void and of no force and effect.” See also Philadelphia & Reading Corp. v. United States, 944 F.2d 1063, 1072 (3d Cir.1991) (assessment was void because deficiency notices were not issued); Ventura Consol. Oil Fields v. Rogan, 86 F.2d 149, 153 (9th Cir.1936) (assessment during the period for petitioning the Board of Tax Appeals (now the Tax Court) was illegal and given no effect), cert. denied, 300 U.S. 672, 57 S.Ct. 610, 81 L.Ed. 878 (1937); Yellow Cab Co., 90 F.2d at 701 (assessment while petition was pending before the Board of Tax Appeals was void).
  Reversed.
instruction: What follows is an opinion from a United States Court of Appeals.
  Intervenors who participated as parties at the courts of appeals should be counted as either appellants or respondents when it can be determined whose position they supported. For example, if there were two plaintiffs who lost in district court, appealed, and were joined by four intervenors who also asked the court of appeals to reverse the district court, the number of appellants should be coded as six.
  In some cases there is some confusion over who should be listed as the appellant and who as the respondent. This confusion is primarily the result of the presence of multiple docket numbers consolidated into a single appeal that is disposed of by a single opinion. Most frequently, this occurs when there are cross appeals and/or when one litigant sued (or was sued by) multiple litigants that were originally filed in district court as separate actions. The coding rule followed in such cases should be to go strictly by the designation provided in the title of the case. The first person listed in the title as the appellant should be coded as the appellant even if they subsequently appeared in a second docket number as the respondent and regardless of who was characterized as the appellant in the opinion.
  To clarify the coding conventions, consider the following hypothetical case in which the US Justice Department sues a labor union to strike down a racially discriminatory seniority system and the corporation (siding with the position of its union) simultaneously sues the government to get an injunction to block enforcement of the relevant civil rights law. From a district court decision that consolidated the two suits and declared the seniority system illegal but refused to impose financial penalties on the union, the corporation appeals and the government and union file cross appeals from the decision in the suit brought by the government. Assume the case was listed in the Federal Reporter as follows:
  United States of America,
  Plaintiff, Appellant
  v
  International Brotherhood of Widget Workers,AFL-CIO
  Defendant, Appellee.
  International Brotherhood of Widget Workers,AFL-CIO
  Defendants, Cross-appellants
  v
  United States of America.
  Widgets, Inc. & Susan Kuersten Sheehan, President & Chairman
  of the Board
  Plaintiff, Appellants,
  v
  United States of America,
  Defendant, Appellee.
  This case should be coded as follows:Appellant = United States, Respondents = International Brotherhood of Widget Workers Widgets, Inc., Total number of appellants = 1, Number of appellants that fall into the category "the federal government, its agencies, and officials" = 1, Total number of respondents = 3, Number of respondents that fall into the category "private business and its executives" = 2, Number of respondents that fall into the category "groups and associations" = 1.
  Note that if an individual is listed by name, but their appearance in the case is as a government official, then they should be counted as a government rather than as a private person. For example, in the case "Billy Jones & Alfredo Ruiz v Joe Smith" where Smith is a state prisoner who brought a civil rights suit against two of the wardens in the prison (Jones & Ruiz), the following values should be coded: number of appellants that fall into the category "natural persons" =0 and number that fall into the category "state governments, their agencies, and officials" =2. A similar logic should be applied to businesses and associations. Officers of a company or association whose role in the case is as a representative of their company or association should be coded as being a business or association rather than as a natural person. However, employees of a business or a government who are suing their employer should be coded as natural persons. Likewise, employees who are charged with criminal conduct for action that was contrary to the company policies should be considered natural persons.
  If the title of a case listed a corporation by name and then listed the names of two individuals that the opinion indicated were top officers of the same corporation as the appellants, then the number of appellants should be coded as three and all three were coded as a business (with the identical detailed code). Similar logic should be applied when government officials or officers of an association were listed by name.
  Your specific task is to determine the total number of appellants in the case that fall into the category "private business and its executives". If the total number cannot be determined (e.g., if the appellant is listed as "Smith, et. al." and the opinion does not specify who is included in the "et.al."), then answer 99.