Each retailer shall file a tax return with the department on forms prescribed by the department. Annual returns are required if the retailer’s yearly tax liability is less than two hundred fifty dollars. Quarterly returns are required if the retailer’s yearly tax liability is at least two hundred fifty dollars but less than six thousand dollars. Monthly returns are required if the retailer’s yearly tax liability is at least six thousand dollars. The return shall contain a declaration by the person making the return to the effect that the statements contained in the return are true and are made under penalties of law, which declaration has the same force and effect as a verification of the return and is in lieu of such verification. The return shall show such information as the department reasonably requires for the proper administration and enforcement of the Compressed Fuel Tax Act. The retailer shall file the return in such format as prescribed by the department on or before the twentieth day of the next succeeding calendar month following the reporting period to which it relates. If the final filing date falls on a Saturday, Sunday, or legal holiday, the next secular or business day is the final filing date. The return is filed on time if transmitted or postmarked before midnight of the final filing date.