I saw this joke in the comments section of one of the blogs I follow. I thought it was pretty funny.

At the end of the year, the IRS sent an inspector to audit the books of a synagogue. While he was checking the books, he said to the Rabbi, “I notice you buy a lot of candles. What do you do with the candle drippings?”

“Good question,” noted the Rabbi. “We save them and then send them back to the candle maker, and every now and again they send us a free box of complete candles.”

“Oh,” replied the auditor, somewhat disappointed that his unusual question had a practical answer. On he went in his obnoxious way, “What about all these matzo purchases? What do you do with all the crumbs?”

“Ah, yes,” replied the Rabbi, realizing that the inspector was trying to trap him with an unanswerable question. “We collect them and send them back to the manufacturer, and every now and again they send us a free box of complete matzo.”

“I see,” replied the frustrated auditor, now thinking harder about how he can fluster the know-it-all Rabbi. “Well Rabbi, what do you do with all the leftover foreskins from the circumcisions that you perform?”

“Here too we do not waste,” answered the Rabbi. “We save up all the foreskins and send them to the Internal Revenue Service, and every now and again they send us a back a complete dick.”