A clause in a gas supply contract which provides that a minimum quantity of gas be paid for, whether or not delivery is accepted by the purchaser. Most contracts contain a time period in which the buyer may take later delivery of gas without penalty. Not generally included in contracts written today. Some buyers will pay the seller a fee (often large) to buy out the contract (usually an old contract), so they are not required to take the gas. Often abbreviated to TOP by companies, but should be written in full.