If you’d like to cancel your energy contract with British Gas, simply contact them to let them know you’ll be leaving.  They’ll send you a final meter reading and you’ll be required to pay off the rest of your balance.
British Gas charges home energy customers £75 per fuel for cancellations.
Businesses should avoid breaking their business energy contracts as this is likely to cause substantial penalty fees. Companies wanting to switch suppliers at the end of their contract are required to provide at least 30 days’ notice.