The penalty for late filing of an IRS K-1 form varies depending on the circumstances. If the K-1 form is being filed as part of a partnership or S corporation tax return, and the taxpayer has reasonable cause for not filing on time, no penalty will be imposed. However, if the K-1 form is filed late without reasonable cause, the penalty can be imposed at a rate of $195 per month for each partner or shareholder, up to a maximum of 12 months. Additionally, if the late filing is deemed to be intentional disregard of the filing requirements, the penalty can increase to $260 per month, per partner or shareholder, with no maximum limit. It's important to note that these penalties can vary, so it's advisable to consult with a tax professional for specific guidance based on your situation.