The Internal Revenue Service’s annual list of the “dirty dozen” tax schemes that Americans should avoid includes a warning about illegal efforts involving charitable organizations and charitable-tax deductions.

The IRS said it continues to observe the misuse of tax-exempt organizations. “Abuse includes arrangements to improperly shield income or assets from taxation and attempts by donors to maintain control over donated assets or income from donated property,” the IRS said.

The tax agency said it “also continues to investigate various schemes involving the donation of non-cash assets, including situations where several organizations claim the full value for both the receipt and distribution of the same non-cash contribution.”

Often, the IRS said, “these donations are highly overvalued, or the organization receiving the donation promises that the donor can repurchase the items later at a price set by the donor.”

The IRS continued: “The Pension Protection Act of 2006 imposed increased penalties for inaccurate appraisals and set new definitions of qualified appraisals for taxpayers claiming charitable contributions.”

The tax agency said that “tax schemes are illegal and can lead to imprisonment and fines for both scam artists and taxpayers. Taxpayers pulled into these schemes must repay unpaid taxes plus interest and penalties. The IRS pursues and shuts down promotors of these and numerous other scams.”