Tax-season gripes regarding the Internal Revenue Service are about as American as baseball and apple pie. But we bet you've never expressed your frustration quite like NFL player Evan Mathis did on Wednesday.

The Philadelphia Eagles offensive lineman posted the photo you see below to Instagram. As one can't help but notice, he appears to be taking a leak on something that's obviously IRS property. Please take special note of the "audit this" caption.

Image courtesy of Evan Mathis

Just what precisely Mathis is so pissed off about — other than just like, taxes in general, man — isn't quite clear. But one thing is obvious: He's not exactly having guilt pangs over the stunt:

How high are we counting? RT @dcfanaticsblog: Evan Mathis will be apologizing later today. Count on that. — Evan Mathis (@EvanMathis69) May 15, 2013

UPDATE: Mathis told SI.com on Thursday that he if reveals whether or not he actually peed on the sign he'll "lose too much street cred," and that he's "being audited right now" for his 2011 taxes.

Image by NFL via Getty Images