For information on estimated tax payments, including penalties that apply if the corporation fails to make required payments, see the instructions for line 15 on page 9. If the corporation overpaid estimated tax, it may be able to get a quick refund by filing Form 4466, Corporation Application for Quick Refund of Overpayment of Estimated Tax. To apply for a quick refund, file Form 4466 before the 16th day of the 3rd month after the end of the tax year, but before the corporation files its income tax return. Do not file Form 4466 before the end of the corporation's tax year. Interest and Penalties Interest.
Interest is charged on taxes paid late even if an extension of time to file is granted.
The interest charge is figured at a rate determined under section 6621. Penalty for late filing of return. The penalty will not be imposed if the corporation can show that the failure to file on time was due to reasonable cause. Corporations that file late must attach a statement explaining the reasonable cause. Penalty for late payment of tax.