Each taxpayer is required to keep, for a period of 4 years, unless permission is obtained from the Comptroller to destroy the records after a shorter period of time, all records in connection with: Sales and purchases; and Gross receipts subject to the admissions and amusement tax. The records shall be adequate to distinguish taxable sales, purchases, or gross receipts from nontaxable sales, purchases, or gross receipts. This requires keeping all invoices, bills of lading, purchase orders, sale slips, cash register tapes, meter readings, invoices, contracts, tickets, billing slips, journals, ledgers, inventory records, bank records, and advertising and promotional literature. In the event a vendor elects to assume or absorb all or part of the sales and use tax on any retail sale, the records shall also distinguish sales in which the vendor assumed or absorbed the tax from sales in which the vendor did not assume or absorb the tax. Exempt Sales. If sales for resale are made, resale certificates obtained from the purchaser shall be retained. For sales and use tax purposes, if a sale to an exempt purchaser is made, an exemption number issued to the purchaser shall be a part of the sales record. For every sale of medical cannabis, as defined in COMAR 03.06.01.47, the qualifying patient or caregiver’s registration number shall be a part of the sales record. Sales to contractors of material to be incorporated into exempt jobs shall be supported by written statements from the contractors, identifying the jobs and certifying that the materials are for incorporation into the jobs. If a sale is subject to a multiple points of use certificate, the certificate and all applicable records obtained from the purchaser shall be retained by the vendor. If a sale is subject to a multiple points of use certificate, the buyer shall retain records as they exist at the time of sale supporting: The apportionment reflecting the primary use location in the State; and The method of apportionment. The taxpayer is required to make records available for inspection and examination by the Comptroller or authorized representative at any time during business hours. If the taxpayer fails to keep the records required, the Comptroller may compute the taxes due by using a factor that the Comptroller develops by: A survey of the business of the person including any available records; A survey of other persons engaged in the same or similar business; or Other means. The computation of the tax under §I of this regulation is presumptively correct.