Appellant Taxpayers were the owners of all or a portion of the oil, gas and other minerals in, on, and under each of their real property located in the counties party to this lawsuit. Taxpayers filed a complaint against the Counties, seeking declaratory judgment and injunctive relief, alleging that an ad valorem property tax was an illegal exaction. The circuit court concluded that Taxpayers had failed to make a proper illegal-exaction challenge and dismissed their lawsuit. The Supreme Court affirmed, holding that the circuit court was correct in dismissing the Taxpayers' complaint where (1) the crux of Taxpayers' argument was that the tax assessed against them was illegal because the assessment was flawed; and (2) the Taxpayers' avenue of relief for its assessment grievance lay with each county's equalization board.

The issue before the Supreme Court was whether the deduction in RCW 82.04.433(1) applies to reduce Business and Occupation (B&O) taxes for manufacturing activities. Plaintiff Tesoro Refining and Marketing Company owns and operates a refinery in Washington state from which it processes crude oil from Alaska, Canada and other sources. The legislature created a tax deduction for the amount of tax "derived from the sales of fuel for consumption outside the territorial waters of the United States." On its monthly tax returns from 1999-2007, Tesoro reported its fuel sales on both the "Manufacturing" B&O tax line and the "Wholesaling and Retailing" B&O tax line. After completing an audit of the refinery, Tesoro requested a partial tax refund claiming the deduction against amounts paid in B&O tax on manufacturing from 1999 through 2004. The request was denied by the Department of Revenue's (DOR) appeals division on the ground that the deduction applied only to taxes paid under the "wholesaler and retailer" B&O tax line. Tesoro appealed to the superior court; the Court of Appeals held that the company could deduct the amount of its "offshore" bunker fuel sales from its B&O taxes. Upon review, the Supreme Court reversed the Court of Appeals and reinstated the superior court's grant of summary judgment to the DOR: "the plain language of RCW 82.04.433(1) … indicates that the B&O deduction applies only to ... taxes on wholesale and retail sales, not on manufacturing."

Appellants Ismael Chavez and Dolores Mercado (collectively Chavez) appealed the district court's granting their petition for judicial review, claiming that their original complaint should not have been converted into a petition for judicial review. Canyon County cross-appealed the district court's decision that the flat fee included on the County's notice of pending issue of tax deed was in violation of I.C. 63-1005(4)(d) requiring an itemized statement. In 2009, Chavez filed a class action complaint seeking a declaratory judgment and damages. Chavez alleged that Canyon County had violated a requirement in Idaho Code section 63-1005(4)(d) for an itemized statement of all costs and fees in its notice prior to an issuance of treasurer's tax deeds on two parcels of land they owned. In its Notice of Pending Issue of Tax Deed on the two parcels, the County charged a $500 flat fee for administration costs. In 2010, upon a motion for summary judgment, the district court denied the motion and found Chavez had failed to follow the proper procedures. The court allowed Chavez fourteen days to file the required Petition for Judicial Review. In its review, the Supreme Court held that the district court improperly converted Chavez's declaratory action into a petition for judicial review and was without jurisdiction to rule on the petition for judicial review. Furthermore, the Court declared the notices of pending issue of tax deed to be deficient and void and the corresponding fee was found as moot.

Defendant-Appellant International Bancshares Corporation (IBC) appealed the judgment of the district court in favor of Plaintiff-Appellee MCC Management of Naples (Colliers). The Colliers sued for breach of contract and fraud in a dispute over tax benefits. The dispute arose over the parties' disagreement over the entitlement to $16 million in benefits that accrued over a period of years in Local bank. Brothers and investors Miles and Barron Collier owned Local at the time the tax benefits arose. IBC now owns the bank. Local bought troubled loan assets. An agency (now the FDIC) guaranteed the value of the assets. In return, Local had to "share" some of its profits. When Congress repealed the deductions Local claimed on the losses from the assets, Local stopped paying its share from those assets and sued in federal court. The FDIC counterclaimed for non-payment. The Townsend Group had purchased Local Bank from the Colliers while the lawsuit was pending. Townsend required the Colliers promise to indemnify Townsend/Local in the event the FDIC won the lawsuit for more than the potential liability in the suit. Local eventually settled the suit for approximately $25-27 million. Townsend/Local and the Colliers signed a Resolution and Modification Agreement from which the Colliers claimed entitlement to the aforementioned tax benefits. Furthermore, through the "excess basis deduction," Local claimed a deduction on principal payments made to the FDIC and for attorney's fees. In addition to the dispute over the tax benefits, Local's former "tax director" quit over what she believed was the bonus owed to her for discovering the excess basis deduction. She began consulting for the Colliers and notified them of the millions in deductions that Local claimed. IBC counterclaimed against the Colliers, and added third-party claims against the former tax director for breaching confidentiality and tortious interference with contract. The Colliers and tax director prevailed after a jury trial. IBC appealed, arguing it was entitled a judgment as a matter of law. But after review, the Tenth Circuit found no error in the district court's findings at trial.

Husband and wife filed returns for tax years 1997-1999 reporting zero income, despite having reportable income. Based on advice from their dentist and their own research, they concluded that no provision of the Internal Revenue Code imposed liability on them for taxes, and attached this explanation to their returns. They succeeded in stopping their employer from withholding taxes claiming exemptions and having the employer treat them as independent contractors, not subject to withholding of social security and medicare taxes. Between 2000 and 2008, despite reportable income asserted by the government to exceed $100,000 in each year, they filed no returns and took steps that made it more difficult for the government to track their assets. Between 1999 and 2007, the IRS repeatedly informed them that their position was frivolous and specifically warned of criminal sanctions. Convicted of conspiracy to defraud the U.S., 18 U.S.C. 371 (2006); attempted evasion of payment of tax, 26 U.S.C. 7201; and four counts of willful failure to file income tax returns, each was sentenced to 36 months in prison. The First Circuit affirmed, reasoning that the convictions were based on defendants' conduct, not guilt by association.

Taxpayer took business and individual tax deductions for the cost of "Loss of Income" insurance policies. The policies were back-dated, had a high premium to coverage ratio, were described as tax-savings products, and allowed taxpayer access to and control over the funds. A significant part of the premium was invested for later distribution to the policy holder. He was convicted of: subscribing a false tax return, 26 U.S.C. 7206(1); attempting to evade taxes, 26 U.S.C. 7201; and conspiracy to defraud the government, 18 U.S.C. 371. The Sixth Circuit affirmed, holding that the government presented sufficient evidence of the crimes. The court rejected a challenge to prior bad acts evidence and an argument that the government was required by the nature of the charges to forgo charging him under the general crime of conspiracy to defraud the U.S. The district court properly ordered payment of restitution for the personal income taxes of his co-conspirator.

Petitioner-Appellant Jean Mathia is the widow of Doyle Mathia, who was a limited partner in Greenwich Associates. Greenwich was a partnership that incurred losses that were passed through to the couple’s income tax returns for the years 1982–84. After an investigation of numerous related tax shelters, the Commissioner of Internal Revenue disallowed these losses. Petitioner was assessed more than $150,000 in taxes following lengthy administrative and judicial proceedings involving the partnership. Petitioner appealed to the United States Tax Court to challenge the assessments as untimely, and to assert that the government bore the burden of proof in establishing timeliness. The Tax Court denied the appeal. On appeal to the Tenth Circuit, Petitioner contended the tax assessments were untimely because the relevant statute of limitations had run. The Tenth Circuit concluded that Petitioner's contention turned on whether Mr. Mathia entered into a settlement agreement under the tax code that resolved his partnership tax liability on an individual basis. The Court agreed with the tax court that he entered into no such agreement which would have qualified under the tax code as a settlement of Mr. Mathia's liability as an individual partner. Therefore, the Court concluded the assessments were timely and properly applied by the IRS.

Debtor filed for bankruptcy on September 25, 2007, and was granted a discharge by the bankruptcy court pursuant to 11 U.S.C. 727. Debtor then filed an adversary proceeding in the bankruptcy court against the Commission on December 3, 2008, seeking a declaration that two years of her pre-petition state income tax debts were subject to that discharge. The bankruptcy court dismissed debtor's complaint because she failed to timely file her Mississippi tax returns, her returns were not "returns" for the purposes of discharge under the Bankruptcy Code. The court agreed and concluded that debtor's 1998 and 1999 tax returns did not comply with the filing requirements of applicable Mississippi tax law and were, therefore, not "returns" for discharge purposes. Accordingly, the court affirmed the judgment of the bankruptcy court.

In three challenged orders, the Commission addressed a "traffic pumping" scheme in which the holder of the filed tariff entered into contractual arrangements with conference calling companies and charged the interexchange carrier the tariff rate for providing switched access service. Farmers, the holder of the tariff, petitioned for review. As a threshold matter, Farmers, joined by intervenor, contended that the Commission lacked authority to overturn its decision in Farmers I because it failed, as 47 U.S.C. 405(b) required, to act within 90 days on Qwest's petition for partial reconsideration and consequently, Farmers I became a final appealable order. The court held that the contention was based on a misreading of the statute. The merits question was whether the Commission properly determined that Farmers was not entitled to bill Qwest for access service under Farmers' tariff because Farmers had not provided interstate "switched access service" as that term was defined in Farmers' federal access tariff. The court held that the Commission, upon considering factors within its expertise, could reasonably conclude that Farmers' relationships with the conference calling companies had been deliberately structured to fall outside the terms of Farmers' tariff and therefore reasonably rejected such services as tariffed services. Therefore, deference to the Commission's determination was appropriate. Accordingly, the court denied the petition.

The Association sought extraordinary writ relief from the court, arguing that two measures intended to stabilize school funding by reducing or eliminating the diversion of property tax revenues from school districts to the state's community redevelopment agencies, was unconstitutional. At issue was whether the state Constitution (1) redevelopment agencies, once created and engaged in redevelopment plans, have a protected right to exist that immunized them from statutory dissolution by the Legislature; and (2) redevelopment agencies and their sponsoring communities have a protected right not to make payments to various funds benefiting schools and special districts as a condition of continued operation. Answering the first question "no" and the second "yes," the court largely upheld Assembly Bill 1X 26 and invalidated Assembly Bill 1X27. The court held that Assembly Bill 1X 26, the dissolution measure, was a proper exercise of the legislative power vested in the Legislature by the state Constitution. The court held that Assembly Bill 1X 27, the measure conditioning further redevelopment agency operations on additional payments by an agency's community sponsors to state funds benefits schools and special districts, was invalid.