I use Quidco and Top Cashback websites. They give you cashback on online purchases that you would have made anyway. They also have voucher codes so you can find yourself getting a discount AND cashback. You just need to go to their website first, then search for the retailer you want to use and click on the offer and the get cashback button. This will then take you into the retailer’s website and Quidco or Top Cashback will register your visit. Once the retailer agrees and pays these sites commission, you will be paid cashback. It is really easy to do and I have received hundreds in cashback over the last two years through these sites!
Quidco takes the first £5 of any cashback you earn as a membership fee but Top Cashback does not. I also find that Top Cashback offers slightly more cashback than Quidco, for example if Quidco are offering 8% with Argos, Top Cashback might offer 8.1%. I check both before I purchase online and 9/10 I use Top Cashback.
The other thing to bare in mind with both of these sites is that you do have to wait sometime for your cashback. With some retailers you have to wait months but you are kept up to date with the status of your payment and it is lovely to get a surprise credit in your account months down the line!
Both sites also have mobile apps so you can also earn cashback instore. Quidco allows you to check in and be paid pence for walking into a store and Top Cashback allows you to upload a picture of your grocery shop for cashback.