According to the Maryland Comptroller's office, if you fail to file your Maryland Form 502B (Application for Extension to File Personal Income Tax Return) by the original filing deadline (usually April 15th), you may be subject to penalties and interest on any taxes owed. The penalty for late filing is typically 5% per month, up to a maximum of 25% of the total tax due. In addition, interest will accrue on any unpaid taxes at a rate of 0.5% per month. It's important to note that these penalties and interest apply only to the amount of unpaid tax, not the entire tax liability. If you do not owe any additional tax or are receiving a refund, there is typically no penalty for filing your Form 502B late.