The penalty for late filing of a K-1 form can vary depending on several factors, including the length of the delay and whether it was a deliberate attempt to avoid reporting. The standard penalty for late filing of a partnership or S corporation K-1 form is $270 per form per month, up to a maximum of $3,240 per form. However, if the failure to file the K-1 form is deemed to be intentional and a deliberate attempt to avoid reporting income, the penalty can increase significantly, resulting in fines of up to 75% of the total tax owed. It's important to note that penalties can vary depending on the specific circumstances, so it is always advisable to consult with a tax professional or the IRS for accurate and up-to-date information regarding penalties for late filing of K-1 forms.