Those unique stage outfits that ABBA wore in their 70s hey day were apparently a tax dodge.

In the upcoming ABBA: The Official Photo Book, co-founder Bjorn Ulvaeus says Swedish tax laws permitted the cost of costumes to be tax deductible only if they couldn't be worn off stage.  Of course, no one in their right mind would dress the way ABBA dressed walking down the street.

He says, "In my honest opinion we looked like nuts in those years.  Nobody can have been as badly dressed on stage as we were."

Back in 2007, the Swedish government accused him of underpaying millions in taxes, but he was able to get the charge dropped in part because of that loophole.