If you purchase tickets from unauthorised sellers, the tickets may turn out to be fake or may not arrive.
Even if the ticket that you've bought from an unauthorised seller is genuine, you could still be refused entry to the event if the resale of tickets is not permitted.
Fraudsters are becoming increasingly sophisticated in their operations and can set up very convincing websites that look very similar to genuine ones.
You can get advice on safe online shopping here.
If you feel you have been ripped off when buying theatre tickets, please report it by completing the form below and sending this along with copies of tickets and receipts to the Society of London Theatre.