The rules are a little different for companies that are classified as 'microbusinesses'. These are small companies that either:
Use no more than 100,000 kWh of electricity per year
Use no more than 293,000 kWh of gas per year
Have 10 or fewer employees and turn over no more than €2 million per year
If you qualify as a microbusiness, your supplier must provide you with extra support with switching. For example, they should put the end-date and notice period for your contract on all bills, and tell you your annual energy consumption and how your old tariff compares with their latest options.