Taxpayers appeal from an order of the Tax Court which upheld the Commissioner’s findings of deficiency and ordered additions to tax. We affirm, and impose sanctions.

Taxpayers petitioned the Tax Court for review of deficiencies in their income tax plus negligence penalties assessed by the Commissioner pursuant to 26 U.S.C. § 6653 . The deficiencies were based upon the disallowance of taxpayers’ contributions to the Universal Church of God, a charter church of the Universal Life Church, Inc.

The Tax Court refused to admit, on the grounds of hearsay, two letters which purportedly acknowledged receipt by the parent church of the taxpayers’ contributions. The court also refused to admit copies of receipts which the taxpayers allegedly received from the parent church acknowledging their contributions, because taxpayers did not establish a proper foundation for admission of those receipts.

The Tax Court found that the taxpayers had failed to carry their burden of showing that the Commissioner incorrectly disallowed the deductions, that the Commissioner incorrectly assessed a deficiency or that the imposition of the addition to tax was in error. The court also held that, because taxpayers should have known that their case was frivolous, a $4,000 penalty was appropriate under 26 U.S.C. § 6673 .

Contributions to the Universal Life Church are tax deductible under 26 U.S.C. § 170 , see Universal Life Church Inc. v. United States, 372 F.Supp. 770 (E.D.Cal.1974), but exemptions for parent churches do not automatically carry over to local charters. Kalgaard v. C.I.R., 764 F.2d 1322, 1323 (9th Cir.1985); Hall v. C.I.R., 729 F.2d 632, 634 (9th Cir.1984). The copies of checks which taxpayers presented to support their claims of deduction were payable to “Universal Church of God” with the initials “ULC” squeezed onto the same line. The copies showed only the front and not the back side of the checks. The Tax Court accorded no eviden- *1083 tiary weight to the copies of the checks. The taxpayers also offered two letters from Universal Life Church officials which acknowledged receipt of taxpayers’ contributions. The letters were written in 1983 although the contributions were allegedly made in 1980 and 1981. Furthermore, taxpayers’ witness did not have and could not produce church records which could support the letters of receipt. The Tax Court, therefore, properly refused to admit the letters. See Fed.R.Evid. 1006; Kalgaard, 764 F.2d at 1323-24 .

Finally, the court refused to admit individual receipts offered as evidence of the contributions because taxpayers’ witness had no personal knowledge of the contents of the receipts.

Given taxpayers’ evidentiary failures, the Tax Court’s findings that the checks had been altered, and that taxpayers’ contributions were not subject to the control of the parent church, are not clearly erroneous. Those findings are sufficient to support its conclusion that the taxpayers failed to sustain their burden of showing that the Commissioner’s assessment of deficiency was in error. See Tax Court Rule 142(a).

Taxpayers argue that because the Tax Court is not an Article III court, it cannot have jurisdiction oyer constitutional questions. Taxpayers’ argument is frivolous; we have often upheld Tax Court decisions which were based on a constitutional inquiry. See, e.g., Kalgaard, 764 F.2d at 1324 ; McCoy v. C.I.R., 696 F.2d 1234, 1236 (9th Cir.1983); Edwards v. C.I.R., 680 F.2d 1268, 1270 (9th Cir.1982). Furthermore, Congress has provided taxpayers with a choice of forums in which to raise their disputes with the Commissioner. Taxpayers chose to proceed in Tax Court rather than pay the deficiency assessed and sue in federal district court for a refund. See 26 U.S.C. §§ 7422 , 7442.. They cannot now complain about their choice to proceed in Tax Court.

Taxpayers argue that the imposition of a penalty for a frivolous, meritless petition is an unconstitutional infringement on their First Amendment right to petition the government for redress of grievances. But the right to petition protected by the First Amendment does not include the right to maintain groundless litigation. See Bill Johnson’s Restaurants, Inc. v. NLRB, 461 U.S. 731 , 103 S.Ct. 2161, 2170 , 76 L.Ed.2d 277 (1983).

The Commissioner is permitted to impose an addition to tax under 26 U.S.C. §§ 6653 (a)(1) and (2) where the Commissioner assesses a deficiency because of taxpayer negligence or willful failure to pay tax. Given the lack of credible evidence which taxpayers presented here to support their assertion of deductibility of their contributions to Universal Life Church, the Tax Court was not clearly erroneous in upholding the Commissioner’s assessment of an addition to tax. See Kalgaard, 764 F.2d at 1324 .

The Tax Court is also authorized to impose a penalty for frivolous petitions. 26 U.S.C. § 6673 . That court found the taxpayers’ conduct to be frivolous and vexatious. This court has frequently affirmed such penalties. See Gattuso v. Pecorella, 733 F.2d 709, 710 (9th Cir.1984); McCoy, 696 F.2d at 1235 ; Edwards, 680 F.2d at 1271 . The Tax Court has the power to impose sanctions against willful abuse of the court meant to frustrate tax collection. The court’s judgment is affirmed.

On appeal, the taxpayers’ counsel knew that their position was frivolous. See Larsen v. C.I.R., 765 F.2d 939 (9th Cir.1985); Kalgaard, 764 F.2d at 1324 (same counsel as this case); Hall, 729 F.2d at 633 (same counsel). The Tax Court did not impose sanctions here because of the ineptitude of the pro se litigants. Rather, it imposed sanctions because the taxpayers abused the court system. Their transparent plan to frustrate the revenue by means of sham charitable deductions justified sanctions, and the appeal justifies further sanctions in this court.

The Commissioner is entitled to double costs and $1000.00 attorney fees in this *1084 court together with the judgment in the Tax Court. The taxpayers and their counsel are jointly and severally liable for the costs and fees on appeal.

Affirmed.