The penalty for late filing of Form 1120S, which is used for reporting income and expenses of S corporations, is dependent on the length of the delay: 1. If the corporation fails to file by the original due date (generally March 15th for calendar year corporations), the penalty is $195 for each month or part of the month the return is late, multiplied by the number of shareholders in the S corporation. The maximum penalty is $2,340 per month. 2. If the failure to file continues for more than 60 days after the due date, the minimum penalty is the smaller of $435 or 100 percent of the unpaid tax. 3. If the IRS determines that the late filing was due to intentional disregard of the filing requirements, the penalty can increase to $330 per month for each shareholder. It is important to note that these penalties are subject to adjustment for inflation over time, so it is advisable to consult the most recent tax laws and regulations for accurate and updated penalty information.