A corporation that does not file its tax return by the due date may face a penalty of 5% of the unpaid tax for each month or part of a month the return is late, up to a maximum of 25% of the unpaid tax. The minimum penalty for a return required to be filed in 2026 that is more than 60 days late is the smaller of the tax due or $525. The IRS will not impose the penalty if the corporation can show that the failure to file on time was due to reasonable cause. SDO CPA LLC