If you don’t file your taxes on time, a few things can happen. If you don’t owe anything in your taxes or have a refund coming, there is no penalty for missing the filing deadline. If you do owe the IRS money, you will be charged a rate of 5% of your unpaid tax bill for every month or partial month until your file is returned to a maximum of 25% of what you owe. This kicks in the first day after the tax deadline.