Petitioner Michael Sawukaytis appeals the Tax Court’s decision upholding the determination by the Commissioner of Internal Revenue that there was a deficiency in *31Sawukaytis’s income tax payments for the tax year 1996. Sawukaytis earned close to $70,000 in wages that year but did not file an income tax return. He claims that because the federal income tax is an “excise tax” and because he was told by the government that he did not participate in any excise-taxable activities in 1996, he was not required to file a return. He also claims that the Tax Court erred in denying his motions to review and strike the response given to his request for admissions and that the Tax Court was biased, or at least appeared to be biased, against him. We find no reversible error and affirm the Tax Court’s rulings on the merits.

In addition, Sawukaytis appeals the Tax Court’s decision to award damages in the amount of $12,500 against him, pursuant to 26 U.S.C. § 6673, for filing “several frivolous documents with the Court,” asserting claims “based om stale and meritless contentions,” taking a position in the Tax Court that was “manifestly frivolous and groundless,” and otherwise “wasting] the time and resources of th[e] Court.” The Commissioner has filed a motion in this court requesting that Sawukaytis be sanctioned an additional $4,000 for filing a frivolous appeal. We conclude that both sanctions are merited.

FACTUAL AND PROCEDURAL BACKGROUND

Although Michael Sawukaytis was employed at Ford Motor Company in 1996 and earned $69,699, he did not file a tax return for that year. When the IRS sent him a notice of deficiency, informing him that he owed $13,976 in taxes, plus interest, and a penalty for his failure to file the return, Sawukaytis, acting pro se, filed a petition in the United States Tax Court objecting to the notice of deficiency. He subsequently filed a document styled “request for admissions” that included such statements as: “Respondent is of the opinion that the income tax is a direct tax and, because of the exception provided by the Sixteenth Amendment, need not be apportioned,” and “Respondent is of the opinion that there is no credible evidence to support a position that the income tax is an indirect tax.” The Commissioner declined to admit or deny these “requests,” pointing out that they were not statements of fact that could be admitted or denied. Sawukaytis then filed a motion for review of the Commissioner’s response and various other pretrial motions, all of which were denied by the Tax Court judge assigned to the case.

Sawukaytis continued to represent himself at trial and contended, based upon his reading of the United States Constitution, that the federal income tax is an excise tax. He also asserted that the IRS had informed him by letter that he had not been involved in excise-taxable activity during 1996, from which he concluded that he did not owe any taxes for that year. During Sawukaytis’s testimony, the Tax Court judge warned him that under the Internal Revenue Code, sanctions could be imposed for submitting wholly frivolous arguments and that his arguments appeared to be frivolous.

In his memorandum opinion, the Tax Court judge sustained the Commissioner’s deficiency determination in the amount of $13,976, finding that Sawukaytis had “advanced shopworn arguments characteristic of tax-protester rhetoric that has been universally rejected by this and other courts.” The court also held that Sawukaytis was liable under 26 U.S.C. § 6651(a)(1) for the additional amount of $726 for failure to file a return on the date prescribed, having offered no evidence that his failure to file was due to reasonable cause. Finally, the court found that Sawukaytis’s position was “frivolous and groundless” and that he had *32wasted the time and resources of the court, and imposed a $12,500 penalty under § 6673. Despite the warnings issued by the court during trial and the stiff monetary penalty, the petitioner filed a flurry of post-trial motions, all of which required responses by the respondent and all of which were ultimately denied. Represented for the first time by counsel. Sawukaytis now appeals the judgment of the Tax Court.

ANALYSIS

1. Request for Admissions

Sawukaytis contends that the trial judge erred in refusing to force the Commissioner to respond to his requests for admissions, citing Helvering v. Tex-Penn Oil Co., 300 U.S. 481, 498, 57 S.Ct. 569, 81 L.Ed. 755 (1937), for the proposition that “taxpayers [a]re entitled to know the basis of law and fact on which the Commissioner sought to sustain the deficiencies.” We note that under Tax Court Rule 90, “[a] party may serve upon any other party a written request for the admission, for purposes of the pending action only, of the truth of any matters which are not privileged and are relevant to the subject matter involved in the pending action.” However, a party may do so only if the matters in the request “relate to statements or opinions of fact or of the application of law to fact.” Id. Here, the requests did not relate to facts or the applications of law to facts, but were abstract propositions. Hence, the Tax Court did not abuse its discretion in denying Sawukaytis’s motion to review the Commissioner’s response to his request for admissions or his motion to strike allegations contained in that response.

2. The Deficiency Determination

At trial Sawukaytis stipulated to the fact that he had earned $69,699 in “wage income” from Ford Motor Company in 1996 and that he did not report that income to the IRS, resulting in a deficiency assessment. Beyond that stipulation, not much about this case is clear, despite counsel’s allegation in the brief filed on the petitioner’s behalf that we have before us “the opportunity to settle an area of the law that is fraught with much misunderstanding and confusion” and that our decision in the matter “w[ill] have a far-reaching effect throughout our legal system.” Based on oral argument and statements in the brief, it appears that Sawukaytis no longer challenges the fact of the deficiency or the amount of the IRS assessment.1 His sole contention is that the Congressional Record and the courts—particularly the Supreme Court in Brushaber v. Union Pacific Railroad Co., 240 U.S. 1, 36 S.Ct. 236, 60 L.Ed. 493 (1916)—have declared the income tax an excise tax, yet he was told by the IRS that in 1996 he did not participate in any activity that would subject him to an excise tax.

*33In Martin v. Comm’r., 756 F.2d 38 (6th Cir. 1985), we specifically addressed whether, considering Brushaber, the income tax was properly applied to wage earners. In Martin, the petitioner argued that the Tax Court did not have jurisdiction over him because Brushaber held that “an income tax is really an excise tax, which can only be assessed against those either licensed or incorporated.” Martin, 756 F.2d at 40. We responded:

This argument is baseless. In Brushaber, the Court found the 1913 income tax law to be constitutional. The Court also noted that in Pollock [v. Farmers’ Loan and Trust Co., 158 U.S. 601, 15 S.Ct. 912, 39 L.Ed. 1108 (1895), a case that pre-dated the establishment of the federal income tax in 1913], it had previously found the taxing of income from professions, trades, employments or vocations to be constitutional in the form of an excise tax. In light of the sixteenth amendment, however, all taxation of income, “from whatever source derived,” was found to be constitutional in Brushaber. A multitude of cases following Brushaber have held that the type of revenues and receipts earned by appellant ... constitute taxable income under the Internal Revenue Code ... Appellant’s earnings, which are unchallenged here, constitute gross income under the applicable sections of the Internal Revenue Code. Appellant is therefore liable for income taxes, determined to be due....

Id. Martin thus confirms that, even considering Brushaber, the income tax applies to wage earners.

Sawukaytis nevertheless claims that “this Honorable Court has unequivocally affirmed the position of the United States Supreme Court and the position of the United States Congress” that the income tax is an excise tax, quoting from United States v. Gaumer, 972 F.2d 723, 725 (6th Cir. 1992), in which we noted that “Brushaber and the Congressional Record excerpt do indeed state that for constitutional purposes, the income tax is an excise tax.” However, no reasonable reader of this opinion could construe it as overturning the ruling in Martin. Gaumer was a criminal case in which the defendant, who was indicted for willfully failing to file federal income tax returns, sought to persuade the jury that he did not have the requisite intent because he sincerely believed that he did not have to pay income taxes. As proof, Gaumer wanted to introduce photocopies of three court cases, including Brushaber, which he said had caused him to believe that he did not have to pay taxes. In quoting Brushaber, we clearly did not hold that the income tax is an excise tax but merely indicated that certain language in the case might lead a jury to find that Gaumer honestly believed that he did not have to pay income tax.

We conclude that the petitioner has failed to establish that the Tax Court erred in finding him hable for the amount of the original assessment, as well as the additional amount for failure to file a timely return.

3. Sanctions by the Tax Court

The Tax Court found that Sawukaytis’s position in pressing his petition was “frivolous and groundless,” that he had “wasted the time and resources of [the] Court,” and that he was properly subject to imposition of a penalty of up to $25,000, as authorized under 26 U.S.C. § 6673. The court assessed a penalty of $12,500, a decision that we review for abuse of discretion. See Wolf v. Comm’r., 4 F.3d 709, 716 (9th Cir. 1993). We find no abuse of discretion in this case.

It is well-settled that wages constitute taxable income. See, e.g., Perkins v. *34Comm’r., 746 F.2d 1187 (6th Cir. 1984). Sawukaytis appears to think that he can avoid the weight of precedent and forestall imposition of a penalty under § 6673 simply by claiming that his excise-tax argument has been “judicially endorsed.” In order to avoid paying taxes on the wages he earned from Ford, however, Sawukaytis must show either that taxing wage income like his is unconstitutional, a position that he has never advocated, or that it is not authorized by statute, a position for which he has produced no legal support.

Moreover, we have labeled as frivolous other cases in which the taxpayer claimed that he did not owe taxes on earned income. See id. at 1188 (sanctioning taxpayer under Federal Rule of Appellate Procedure 38 for filing frivolous appeal); Martin, 756 F.2d at 41 (same). Indeed, Sawukaytis was warned by the Tax Court judge that his argument was groundless and that he risked being sanctioned. He persisted nevertheless and now tries to distance himself from cases in which the claims have been deemed frivolous by arguing that, unlike the litigants in those cases, he is not contending that the income tax is unconstitutional. However, just like the litigants in the other cases, he is asserting that the income tax does not apply to his wages. The basis for his argument is no more grounded in law than were those constitutional challenges. Given the amount of research that the petitioner conducted in order to file his pro se pleadings in the Tax Court, and in view of the warnings by the trial judge, Sawukaytis should have been fully aware that the courts have uniformly recognized that wages constitute taxable income for purposes of federal tax law.

We decline to overturn the imposition of the § 6673 penalty below, finding that it was fully justified under all the circumstances of this case. Moreover, we reject out of hand the petitioner’s current allegation that the rulings of the trial judge were the product of bias or that they raise the appearance of bias. This contention is completely unwarranted. It seems to be based on the fact that the Tax Court judge denied various requests of the petitioner, while granting those of the respondent. But, as the United States Supreme Court has noted, “judicial rulings alone almost never constitute a valid basis for a bias or partiality motion.” Liteky v. United States, 510 U.S. 540, 555, 114 S.Ct. 1147, 127 L.Ed.2d 474 (U.S. 1994). Given the groundless nature of both the petition and the petitioner’s advocacy in this case, the rulings of the trial judge simply cannot be said to reflect bias against Sawukaytis.

4. Sanctions by this Court

On appeal, the respondent has filed a motion for sanctions pursuant to 28 U.S.C. § 1912 and Federal Rule of Appellate Procedure 38, under which we are authorized to award damages and costs against an appellant who has been found to have filed and pursued a frivolous appeal. Certainly, we have no interest in chilling the right of any party to appeal, as we noted in Wilton Corp. v. Ashland Castings Corp., 188 F.3d 670, 677 (6th Cir. 1999). On the other hand, we have not hesitated to impose sanctions when the appeal is “wholly without merit.” Id. Specifically, we have warned that we would impose sanctions in cases in which litigants argue that income from wages cannot be taxed. See Martin, 756 F.2d at 41 (“In future such cases this court will not hesitate to award damages when the appeal is frivolous .... ”); Perkins, 746 F.2d at 1188-89 (“Litigants are warned that in future cases in which the lower court has clearly explained, as it has here, the frivolous nature of the taxpayer’s claim that earned income is not taxable, we will not hesitate to *35award actual attorney fees to the Commissioner under Rule 38 as it has been uniformly construed.”).

Here, Sawukaytis asserts that his appeal is not wholly without merit because of “this Honorable Court’s published dicta [in United States v. Gaumer ] which categorically states that ‘for constitutional purposes, the income tax is an excise tax.’” As noted above, however, Gaumer does not hold that the income tax is an excise tax; it simply recognizes that a jury, cognizant of language in Brushaber, might understand why a delinquent taxpayer could think so. In fact, the Gaumer court specifically said that “as a legal matter, the exhibits do not validate Mr. Gaumer’s views [that income taxes are excise taxes and that he was not engaged in any excise-taxable activity].” Gaumer, 972 F.2d at 725. We reject as patently unreasonable the petitioner’s argument that the Gawmer opinion converts his groundless claim into “a colorable issue.” To the contrary, we find that Sawukaytis’s appeal was obviously frivolous and, therefore, grant the respondent’s motion for sanctions.

The Commissioner’s request for an award of $4,000 is based on records of the Tax Division of the Department of Justice showing that the average expense incurred in the defense of taxpayer appeals in which sanctions were awarded during 1998 and the first half of 1999 was approximately $4,900. We have approved awarding lump-sum damages under Rule 38, rather than requiring a “detailed accounting” of expenses. See, e.g., Schoffner v. Comm’r, 812 F.2d 292, 294 (6th Cir. 1987) (awarding $1,200 based on the average award in a recent two-year period). In addition, we have found $4,000 to be a reasonable penalty in at least two recent unpublished decisions in so-called “tax protester” cases. See United States v. Martin, 19 Fed.Appx. 345, 346, 2001 WL 1126126 at *1 (6th Cir. 2001); (unpublished decision); Lawrence v. United States, 229 F.3d 1152, 2000 WL 1182452, at *3 (6th Cir. 2000) (unpublished decision). See also Stafford v. United States, 208 F.3d 1177, 1179 (10th Cir. 2000) (imposing $4,000 award to the Commissioner in a frivolous tax case). We conclude that $4,000 is a reasonable penalty here and grant sanctions in that amount.

The Commissioner also requests that the award be assessed against Sawukaytis’s attorney, Robert V. Mackovski, jointly and severally with Sawukaytis. We have noted that “[w]here a client reasonably relies on the advice of counsel, it may be that a sanction for a frivolous appeal is properly imposed on the attorney if the appeal is without merit or substance.” Wilton Corp., 188 F.3d at 677. In addition, 28 U.S.C. § 1927 provides that courts can impose excess costs, expenses, and attorneys’ fees on an attorney who “multiplies the proceedings in any case unreasonably and vexatiously.” We have found that this standard is met “when an attorney knows or reasonably should know that a claim pursued is frivolous.” Tareco Props. Inc. v. Morriss, 321 F.3d 545, 550 (6th Cir. 2003) (internal quotation marks and citation omitted).

It is clear to us, in the wake of oral argument in this case, that Mackovski should have been aware of the frivolous nature of his client’s claim. Moreover, the appellate brief filed on the petitioner’s behalf includes arguments—particularly those relating to bias—that were not argued below, indicating that the attorney has multiplied the quantity, if not the quality, of frivolous issues on appeal. Although it is true that Sawukaytis filed the notice of appeal pro se and might well have pursued an appeal even in the absence of counsel, Mackovski was obligated, once contacted, to render advice discouraging further vexatious litigation. Mackovski *36was certainly not obligated to undertake representation in this case, and his review of the facts, the law, and—most significantly—the Tax Court judge’s warnings on the record regarding the baseless nature of the litigation should have put Mackovski on notice that in pursuing an appeal, he and his client were risking the imposition of additional sanctions by this court. We thus have no difficulty in 'granting the Commissioner’s final request and ordering that the award of $4,000 be imposed jointly and severally on the petitioner and his attorney.

CONCLUSION

For the reasons set out above, we AFFIRM the decision of the Tax Court finding the petitioner liable for the deficiency in income tax, plus interest, and the addition to tax as calculated in the decision entered on June 19, 2002, as well as the award of § 6673 damages to the Commissioner set out in the same order. Moreover, we order imposition of Rule 38 damages in the amount of $4,000 jointly and severally against the petitioner and his attorney of record.