The IRS doesn't specifically have a penalty specifically for the late filing of mileage records. However, failing to maintain accurate mileage records and substantiation can result in penalties for underreporting income or claiming excessive deductions. If the IRS finds that the taxpayer intentionally disregarded the rules, the penalty may be up to 20% of the disallowed amount. Additionally, interest may accrue on any taxes owed due to the underreported income or excessive deductions. It's important to consult a tax professional for personalized advice in specific situations.