The penalty for late filing of printable income tax forms varies depending on the country's tax laws. In the United States, for example, if you do not file your tax return or request an extension by the deadline, you may face a failure-to-file penalty. This penalty is typically 5% of the unpaid taxes for each month or part of a month that the return is late, up to a maximum of 25% of the unpaid taxes. However, the penalty may be waived or reduced if you can show reasonable cause for not filing on time. It's important to note that each country has its own tax laws and penalties, so it is recommended to consult the specific tax laws of your country or seek professional advice for accurate information.