"How have you managed to buy such a luxurious villa while your income is so low?" asked the IRS auditor.
"Well," the taxpayer answered, "while fishing last summer I have caught a large golden fish. When I took it off the hook, the fish opened his mouth and said, 'I am a magical fish. Throw me back to the sea and I'll give you the most luxurious villa you have ever seen'. I threw the fish back to the sea, and got the villa."
"How can you prove such an unbelievable story?"
"Well, you can see the villa, can't you?"