The Internal Revenue Services has sent Microsoft a whopping $28.9 billion bill for back taxes, plus penalties and interest.

According to an SEC filing, the IRS sent the company a Notices of Proposed Adjustment (NOPAs) covering 2004 to 2013. The IRS says Microsoft owes an additional $28.9 billion, plus penalties and interest.

Microsoft believes the IRS is in error and plans to challenge the bill, according to the filing:

In the NOPAs, the IRS is seeking an additional tax payment of $28.9 billion plus penalties and interest. As of September 30, 2023, we believe our allowances for income tax contingencies are adequate. We disagree with the proposed adjustments and will vigorously contest the NOPAs through the IRS’s administrative appeals office and, if necessary, judicial proceedings. We do not expect a final resolution of these issues in the next 12 months. Based on the information currently available, we do not anticipate a significant increase or decrease to our tax contingencies for these issues within the next 12 months.