
    William C. BONKAVICH; et al., Petitioners—Appellants, v. COMMISSIONER OF INTERNAL REVENUE, Respondent—Appellee.
    No. 04-73276.
    United States Court of Appeals, Ninth Circuit.
    Submitted March 23, 2005.
    
    Decided April 11, 2005.
    William C. Bonkavich, Las Vegas, NV, pro se.
    Diane L. Bonkavich, Las Vegas, NV, pro se.
    Donald L. Korb, Acting Chief Counsel Internal Revenue Service, Laurie A. Snyder, Attorney, Richard Farber, Esq., Eileen J. O’Connor, Esq., DOJ—U.S. Department of Justice, Tax Division, Charles S. Casazza, Washington, DC, for Respondent—Appellee.
    Before: B. FLETCHER, TROTT, and SILVERMAN, Circuit Judges.
    
      
       The panel unanimously finds this case suitable for decision without oral argument. See Fed. R.App. P. 34(a)(2).
    
   MEMORANDUM

William and Diane Bonkavich appeal pro se the Tax Court’s decision, following a bench trial, in favor of the Commissioner in their action contesting tax deficiencies for the years 1988 through 1997. We have jurisdiction pursuant to 26 U.S.C. § 7482. We review de novo a Tax Court’s conclusions of law. See Boyd Gaming Corp. v. Comm’r, 177 F.3d 1096, 1098 (9th Cir. 1999). We affirm.

The Tax Court properly sustained the deficiency determination based on Forms 4340 for the years in question. See Hughes v. United States, 953 F.2d 531, 535-36 (9th Cir.1992). Contrary to petitioners’ contention, the IRS officer is not required to provide them with documentary evidence and copies of statutory notices verifying that all procedural steps were properly taken. See Hansen v. United States, 1 F.3d 137,138 (9th Cir.1993) (holding that Form 4340 is probative evidence in and of itself and, shows in the absence of contrary evidence, that notices and assessments were properly made).

The Tax Court properly held that petitioners waived any challenges to the underlying tax liability by failing to adequately contest it in their petition or at trial. See Tax Ct. R. 34(b)(4); Bob Wondries Motors, Inc. v. Comm’r, 268 F.3d 1156,1161 (9th Cir.2001).

Petitioners’ remaining contentions lack merit.

AFFIRMED. 
      
       This disposition is not appropriate for publication and may not be cited to or by the courts of this circuit except as provided by Ninth Circuit Rule 36-3.
     