A BigTex firm that was audited by the state comptroller’s office has filed a suit that could affect the tax payments of any law firm that offers certain employee perks.

The controversy is whether to classify Winstead’s expenses for continuing legal education, attorney occupation taxes and parking as deductible “employee benefits” under the Texas Tax Code or as nondeductible “working condition amounts” under state comptroller rules related to the franchise tax, also known as the margin tax.