The deadline for filing a state income tax return in Indiana is generally April 15th of each year. If this date falls on a weekend or holiday, the deadline may be extended to the next business day. Taxpayers may also file for an extension, which allows for an additional six months to complete their return. However, it is important to note that this extension only applies to the filing of the return, not to the payment of any taxes owed. Taxes must still be paid by the original due date to avoid penalties and interest. Taxpayers should always check the Indiana Department of Revenue's official website for the most current information and any specific details related to their individual circumstances. Being aware of these deadlines can help ensure timely compliance with state tax regulations.