The IRS claimed Van Dusen, a resident of Oakland, Calif., owed $4,838 in income taxes and the parties had settled all issues for 2004 except for the $12,068 related to cat care. The agency also said her recordkeeping did not meet requirements.

Most of Van Dusen's care for the cats was performed for Fix Our Ferals, a section 501(c)(3)2 organization that specializes in the neutering of wild cats. The court found that the cost of cremating a pet cat, bar association dues and fees to the "DMV" were not deductible. Also disallowed was the cost of repairing a wet/dry vacuum and membership dues for Costco, where she purchased many supplies.

While court held that foster-cat care was deductible, Van Dusen's lack of adequate recordkeeping significantly lessened the amount she might have deducted. The court said her methods were fine for amounts of less than $250. For amounts greater than $250, she would have needed contemporaneous acknowledgment from Fix Our Ferals or other groups.

During 2004, Van Dusen, an attorney in private practice, had 70 to 80 cats, including seven pets that roamed her house. Some that were wild or ill were caged and one room was a "feral room." Cat care hiked expenses for water for laundering cat bedding, electricity to support a special ventilation system and garbage collection that included large volumes of cat waste. She had the wet/dry vacuum because of cleaning needs.

The court said it was unclear how Van Dusen arrived at her claimed deductions of $1,381 for supplies, $9,607 for veterinary bills and $1,080 for utilities. And she did not keep separate records for the expense of caring for her own cats. The court rejected the IRS's contention she was an independent cat rescue worker. It said Fix Our Ferals is loosely organized with no office and relies on volunteers and actively encourages them to provide cat care.

The court calculated some allowable expenses, such as the many bags of woodstove pellets purchased from home centers for use as cat litter. Twelve checks to these centers were excluded because Van Dusen did not show the purchases were exclusively for pellets while nine other purchases were accepted.

The court found that 90 percent of veterinary expenses and pet supplies and 50 percent of cleaning supplies were foster-cat expenses and therefore charitable but only to the extent that Van Dusen could demonstrate they were related to cat care.

The court applied the 90-percent and 50-percent thresholds to individual expenses in each of the three categories. If the amount resulting was less than $250 it was deductible; more than $250 was not. Using that method, the court ruled out more than $5,400 in expenses.