The Gas Act 1995

Since 1 March 1996, gas has been supplied to existing customers of British Gas under the terms of a ‘deemed contract’. From this date, new customers who request a supply from any supplier, including British Gas, are supplied under the terms of a ‘supply contract’. Any new customers who receive a supply of gas from a gas supplier without first entering into a contract are supplied under the terms of a ‘deemed contract’ instead (see here).

You are liable for a gas bill if:

•you were a tariff customer of British Gas on 31 January 1996. You will have had a deemed contract with British Gas from 1 March 1996. You are liable to pay for your supply under the terms of the deemed contract which applies to you;
•you entered into a contract with any supplier from 1 March 1996. You are liable to pay for your supply under the terms of the contract;
•you have a deemed contract with a supplier that started after 1 March 1996.