Quidco works exceptionally well if you use it right. In 18 months, I've had £250 cashback with only one transaction that didn't appear. And that was credited after I submitted an enquiry. Each merchant is rated for tracking reliability and payment speed.

The tracking works, I think, using cookies. If you have previously visited a merchant through somebody else's affiliate link then that is likely to take precedence and they will get the commission, not you. The simplest way around this is to use a separate browser for Quidco transactions. You can visit a site to your heart's content in your normal browser, then use a fresh one when you're ready to purchase.

You should also complete the transaction in one smooth effort. And don't phone the merchant until your transaction shows as 'validated' - otherwise it might become an offline transaction and not valid for cashback.