The tax constitutes a debt owed by the purchaser to the City which is extinguished only by payment of the tax to the Director of Finance or to the retailer. When a purchase from a retailer is made within the City the tax shall be paid to the retailer at the time the purchase price is paid. The tax collected or required to be collected by the retailer constitutes a debt owed by the retailer to the City. Should any remittance of tax be made by a retailer prior to sale of cigarettes to a consumer, such remittance shall be considered as an advance payment to be reimbursed by adding the amount of the tax to the price of the cigarettes at the time of sale to the user or consumer.