You aren't required to file an extension if you don't expect to owe additional income tax or if you anticipate receiving a refund.
If you wish to file a Missouri extension, and don't expect to owe Missouri income tax, you may file an extension by filing Form MO-60 , Application for Extension of Time to File. An automatic extension of time to file will be granted until October 15, 2021.
If you receive an extension of time to file your federal income tax return, you will automatically be granted an extension of time to file your Missouri income tax return, provided you do not expect to owe any additional Missouri income tax. Attach a copy of your federal extension (Federal Form 4868) with your Missouri income tax return when you file.
If you expect to owe Missouri income tax, file Form MO-60 with your payment by the original due date of the return.
Remember: An extension of time to file does not extend the time to pay. A 5 percent addition to tax will apply if the tax is not paid by the original return's due date.