Ind. Code § 6-3-4-5

Sec. 5. When a return of tax is required pursuant to sections 1 and 3 of this chapter, the taxpayer required to make such return shall, without assessment or notice and demand from the department, pay such tax to the department at the time fixed for filing the return without regard to any extension of time for filing the return. In making a return and paying tax for any taxable year, a taxpayer shall take credit for any tax previously paid by him for such taxable year.