1. The director of revenue may grant a reasonable extension of time for payment of tax or estimated tax or any installment thereof, or for filing any return, declaration, statement, or other document required in sections 143.011 to 143.996 on such terms and conditions as he may require. Except for a taxpayer who is outside the United States, no such extension for filing any return, declaration, statement, or document, shall exceed six months.

2. If a taxpayer has been granted an extension of time for filing his or its federal income tax return, the filing of a copy of the extension or the form relating to an automatic extension with the director of revenue shall automatically extend the due date of the income tax return required by sections 143.011 to 143.996.

3. If a taxpayer has been granted an extension of time for paying his or its federal income tax, the filing of a copy of the extension with the director of revenue shall automatically extend the time for the payment of the tax required by sections 143.011 to 143.996.

4. If the time for filing a return is extended under subsection 2, but the time for payment is not extended under subsection 3, the taxpayer shall pay, on or before the date prescribed for the filing of the return (determined without regard to any extensions of time for such filing), the amount properly estimated as his or its tax for the taxable year.