A recent criminal case involving wealthy donors, religious groups and secret kickbacks of donations provides an object lesson in how not to give to charity.

The government contends that two men solicited millions of dollars in contributions to charitable organizations by promising to secretly refund large portions of those gifts, typically 80% to 95%, to donors, who would then deduct the full amount of their original gifts on their tax returns. One of those men and another individual recently pleaded guilty, and others accused of wrong doing are scheduled to face trial later this year. The government is targeting more than 100 donors as part of its continuing investigation.

While most contributors play by the rules, law-enforcement officials say some do not and are robbing the US. Treasury Department of large amounts of revenue. Sometimes the abuse appears to be intentional, resulting in criminal charges. In other cases, donors may be led astray and may inadvertently run afoul of complex tax-law provisions.

Whatever the case, the Internal Revenue Service has been turning up the heat in recent years on what officials consider to be abuses ranging from fabricating deductions to making improper noncash gift valuations.

According to the latest IRS data, more than 41.4 million individual income-tax returns claimed charitable donations for 2006. Their donations totaled a record $173.02 billion, up 0.6% from the prior year.