Jay and Elizabeth Karpa appeal from the Tax Court's decision upholding the Commissioner's proposed imposition of a tax penalty under former I.R.C. Sec. 6661(a). The Karpas argued that the Sec. 6661(a) tax penalty for substantial understatement of tax liability, as applied retroactively to their 1984 return, was unconstitutional as violative of the ex post facto clause. Both parties moved for judgment on the pleadings, and the Tax Court granted the Commissioner's motion. We agree that former Sec. 6661(a) does not violate the ex post facto clause and therefore affirm.

* The Commissioner audited the Karpas' 1984 joint tax return and determined a deficiency of $10,933.07, an understatement of their tax liability of approximately 18%.1 The Karpas paid this amount, plus applicable interest, in July 1986. The Commissioner issued the Karpas a statutory notice of deficiency and proposed a 25% penalty, pursuant to I.R.C. Sec. 6661, for substantial understatement of tax liability for the year 1984. Recent amendments to the Internal Revenue Code (Code) had increased the penalty for substantial understatement of tax liability from 10% of the underpayment to 25% of the underpayment, to be applied to penalties assessed after the effective date of the amendments, October 21, 1986. The Commissioner therefore sought to assess a $2,733.27 penalty under Sec. 6661(a), 25% of the $10,933.07 understatement. The Commissioner also asserted that the Karpas were liable for additions to tax pursuant to former I.R.C. Sec. 6653(a)(1), (2)2 for negligence.

The Karpas petitioned the Tax Court for redetermination of the deficiency. They challenged only the imposition of the 25% penalty under Sec. 6661(a), arguing that retroactive application of the increase to their 1984 tax return violated the ex post facto clause. The Commissioner moved for judgment on the pleadings, and the Karpas filed a cross-motion for judgment on the pleadings.3 The Tax Court followed the established rule that the ex post facto clause applies only to criminal statutes and rejected the Karpas' contention that Sec. 6661 as amended was criminal in nature. Relying on United States v. Halper, --- U.S. ----, 109 S. Ct. 1892, 104 L. Ed. 2d 487 (1989), for guidance, the court found that the penalty under Sec. 6661(a) was not "overwhelmingly disproportionate" to the damages caused by the tax offender and thus the statutory penalty was a civil penalty.

This appeal followed and presents an issue of first impression. The Karpas continue to press their ex post facto argument and, for the first time, raise the contention that retroactive application of the increased penalty under Sec. 6661(a) violates their rights to due process and equal protection of the laws. After reviewing the relevant statutory history of Sec. 6661, we will address the constitutional challenges to the statute.

* Section 6661(a) of the Code, originally passed in 1982 and applicable to tax returns due after December 31, 1982, penalizes the "substantial understatement of income tax."

If there is a substantial understatement of income tax for any taxable year, there shall be added to the tax an amount equal to 25 percent of the amount of any underpayment attributable to such understatement.

I.R.C. Sec. 6661(a) (repealed 1989). As enacted in 1982, Sec. 6661(a) provided for a 10% addition to tax liability. In 1986, Congress passed Sec. 8002 of the Omnibus Budget Reconciliation Act of 1986 (OBRA 1986), increasing the additional assessment from 10% to 25%. OBRA 1986, Pub.L. 99-509, Sec. 8002(a), 100 Stat. 1874, 1951 (1986). The amendment was to apply to "penalties assessed after the date of the enactment of this Act." Id. Sec. 8002(b).4

The legislative history of Sec. 6661 indicates that the principal objective of the section was to deter taxpayers from playing the "audit lottery," that is, taking undisclosed questionable reporting positions and gambling that they would not be audited. See S.Rep. No. 494 (Vol. 1), 97th Cong., 2d Sess., 272-73 (1982), reprinted in 1982 U.S.Code Cong. & Admin.News 781, 1019-1020.5 The Senate Report accompanying OBRA 1986 indicates that a primary purpose of the act was to reduce the budget deficit. S.Rep. No. 348, 99th Cong., 2d Sess. 3-4, U.S.Code Cong. & Admin.News 1986, 3607. Section 8002, which amended I.R.C. Sec. 6661(a) to increase the tax penalty for substantial understatement of income tax liability, was passed along with other revenue enhancing measures in title VIII, subtitle A, of OBRA 1986.

The Karpas challenge the amendment to Sec. 6661(a) as an unconstitutional ex post facto law. Because the 25% penalty applied to penalties assessed after OBRA 1986 was enacted, the increased penalty can apply, as in this case, retroactively to returns due after December 31, 1982, when Sec. 6661 first became effective, but before OBRA 1986 was passed by Congress. This retroactive application of an increase in punishment they claim violates the ex post facto clause. See Collins v. Youngblood, --- U.S. ----, ---- - ----, 110 S. Ct. 2715, 2717-21, 111 L. Ed. 2d 30 (1990); Calder v. Bull, 3 U.S. (3 Dall.) 386, 390-91, 1 L. Ed. 648 (1798) (opinion of Chase, J.).

The prohibition against ex post facto laws applies only to penal legislation that imposes or increases criminal punishment for conduct predating its enactment. See, e.g., Harisiades v. Shaughnessy, 342 U.S. 580, 594, 72 S. Ct. 512, 521, 96 L. Ed. 586 (1952). The ex post facto clause is not applicable to legislation imposing civil disabilities. See, e.g., Johannessen v. United States, 225 U.S. 227, 242, 32 S. Ct. 613, 617, 56 L. Ed. 1066 (1912). Applying these general principles, the Supreme Court rejected an ex post facto challenge to Connecticut's retrospective application of a tax penalty in Bankers' Trust Co. v. Blodgett, 260 U.S. 647, 43 S. Ct. 233, 67 L. Ed. 439 (1923). The statute challenged in Bankers' Trust imposed a 2% tax on the value of estate property for the five years preceding a decedent's death where it appeared that the property was taxable and no state or local tax had been assessed or paid during the year preceding death.6 The Court recognized that the sanction for failure to pay taxes is "usually punitive," and the Connecticut provision for "penalizing a delinquency" was no exception. Id. at 650-51, 43 S.Ct. at 234-35. But the Court held that "[t]he penalty of the statute was not in punishment of a crime," and hence the ex post facto prohibition was simply not implicated. Id. at 652, 43 S.Ct. at 235.

The Court has also warned, however, that the constitutional prohibition against ex post facto legislation may not be avoided by giving civil form to criminal legislation. See Burgess v. Salmon, 97 U.S. (7 Otto) 381, 384, 24 L. Ed. 1104 (1878). In Burgess, the Court held that where federal legislation made it a criminal offense to distribute tobacco without a proper tax stamp, imposition of an additional tax on tobacco when the distributor had already paid the tax under the prior law would violate the ex post facto clause. The Court reasoned that to impose criminal punishment retroactively, or, alternatively, a "penalty" in the form of the increased tax, where "the one was equally authorized with the other," would violate the ex post facto clause. Id.

In Helvering v. Mitchell, 303 U.S. 391, 58 S. Ct. 630, 82 L. Ed. 917 (1938), the Court considered a challenge to a revenue statute imposing a 50% addition to tax on a deficiency, if any part of the deficiency was found to be due to fraud with intent to evade tax. The taxpayer, who had been acquitted on criminal tax evasion charges, alleged that the revenue statute violated the double jeopardy clause by attempting to punish twice the same conduct. Thus the question, which the Court indicated was "one of statutory construction," was whether the statute imposed a "criminal sanction." Id. at 399, 58 S.Ct. at 633. The Court reasoned that the sanction was "provided primarily as a safeguard for the protection of the revenue and to reimburse the Government for the heavy expense of investigation and the loss resulting from the taxpayer's fraud," in holding that the sanction was "remedial," not criminal. Id. at 401, 58 S.Ct. at 634. Congress' intent to impose a civil sanction was clear--a "distinctly civil procedure" was provided for the collection of the additional 50% tax, and the statute at issue was included along with other "Additions to the Tax," as distinguished from "Penalties." Id. at 402, 405, 58 S. Ct. at 634, 637.

The Court's most recent discussion of the distinction between a civil penalty and criminal punishment is contained in United States v. Halper, --- U.S. ----, 109 S. Ct. 1892, 104 L. Ed. 2d 487 (1989). In Halper, the Court again considered when a civil penalty might be deemed "punishment" for double jeopardy purposes. The Court distinguished Mitchell, noting that it did not address the question raised--"whether a civil sanction, in application, may be so divorced from any remedial goal that it constitutes 'punishment' for the purpose of double jeopardy analysis." Id., 109 S.Ct. at 1899. The Halper Court postulated that "in determining whether a particular civil sanction constitutes criminal punishment, it is the purposes actually served by the sanction in question, not the underlying nature of the proceeding giving rise to the sanction, that must be evaluated." Id. at 1901 n. 7. The Court held that double jeopardy would be implicated by an additional civil sanction "to the extent that the second sanction may not fairly be characterized as remedial, but only as a deterrent or retribution." Id. at 1902. Though in a particular case the civil penalty authorized may be so extreme and so divorced from the Government's damages and expenses as to constitute punishment, that case is limited to the situation where the civil sanction is "overwhelmingly disproportionate" to the damages caused by the offender. Id. The Court ruled that a sanction of $130,000, compared to the government's approximated costs of $16,000, was sufficiently disproportionate to constitute a second punishment and a double jeopardy violation. Id. at 1904.

We agree with the Tax Court that the increased tax penalty imposed under former Sec. 6661(a), as amended by Sec. 8002 of OBRA 1986, is a civil sanction; the ex post facto prohibition is not implicated. Under Bankers' Trust, 260 U.S. at 652, 43 S. Ct. at 235, retroactive application of a civil tax penalty does not offend the ex post facto clause. Helvering v. Mitchell and United States v. Halper, although addressing the question in a different context, provide guidance that confirms the civil character of Sec. 6661. Cf. United States v. D.K.G. Appaloosas, Inc., 829 F.2d 532, 540-45 (5th Cir.1987) (following Mitchell and rejecting ex post facto challenge to civil forfeiture statute). As in Mitchell, Congress' inclusion of Sec. 6661 along with the other "additions to tax" in subchapter A of chapter 68 of the Code, rather than with the "crimes" in chapter 75, evinced an intent to impose a civil sanction under Sec. 6661. Though deterrence was a principal goal of Sec. 6661, the amendment increasing the penalty also served to increase government revenues and reimburse the government for investigative and prosecutorial costs.7 See Halper, 109 S. Ct. at 1900 n. 6. We cannot say that a 25% penalty is "overwhelmingly disproportionate" to the damages and expenses caused by taxpayers who substantially understate their tax liability. See id. at 1902; see also Bankers' Trust, 260 U.S. at 651, 43 S.Ct. at 235 (statute's penal effects not "out of relation or proportion" to a decedent's delinquency).

The Karpas' reliance on Burgess v. Salmon is misplaced. The Court there concluded that the ex post facto clause prohibited the government from retroactively increasing the tax that had to be paid to avoid a criminal penalty. Here, no such criminal sanction was implicated. The Karpas' conclusion that characterization of Sec. 6661(a)'s addition to tax as a "penalty" is dispositive and requires reversal of the Tax Court is similarly misplaced. Section 6661(a) imposed a civil sanction, raising no ex post facto concerns.

For the first time on appeal, the Karpas argue that retroactive application of the increased tax penalty under Sec. 6661(a) violates their rights to due process and equal protection of the law. We decline to consider this belated argument, following our general rule that new theories ordinarily will not be considered for the first time on appeal. See, e.g., National Wildlife Fed'n v. Hanson, 859 F.2d 313, 318 (4th Cir.1988). This general rule is applied by courts of appeal reviewing Tax Court decisions. See, e.g., Grauvogel v. Commissioner, 768 F.2d 1087, 1090 (9th Cir.1985). We are unable to say that this is a case justifying departure from that salutary general rule. Neither of the recognized exceptions to its application applies. Proper resolution of the due process and equal protection questions is surely not "beyond any doubt," nor is this a case where " 'injustice might otherwise result' " from our failure to rule on those questions. See Singleton v. Wulff, 428 U.S. 106, 121, 96 S. Ct. 2868, 2877, 49 L. Ed. 2d 826 (1976) (quoting Hormel v. Helvering, 312 U.S. 552, 557, 61 S. Ct. 719, 721, 85 L. Ed. 1037 (1941)). We therefore decline to consider the Karpas' due process and equal protection arguments.

For the foregoing reasons, the judgment entered by the Tax Court for the Commissioner is affirmed.

AFFIRMED.