DENVER (AP) — A marijuana business in Colorado has filed a lawsuit against the Internal Revenue Service for assessing a penalty for paying taxes in cash.

The IRS charges a 10 percent penalty on cash payments for federal employee withholding taxes.

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Because pot is illegal under federal drug law, marijuana businesses have trouble accessing banking services despite federal guidance earlier this year on how banks may accept pot money.

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The Denver Post reports that dispensary Allgreens LLC of Denver is challenging the IRS practice of fining cash payments. The company has filed a petition in U.S. Tax Court.

The IRS says Allgreens owes more than $20,000 in penalties. No hearing date has been set for the petition.

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