Got this email from Quidco for £10 bonus for £10 spend, but it was also eligible on my wife's account even though she didn't get the email, so definitely worth logging in and checking the link to see if it works for you. It's probably directed at people who haven't earned any cashback on their Quidco accounts for a few months.
Also, note the T&C's below about it being awarded for a £10 spend plus VAT and delivery, so to avoid any risk of the bonus not being applied, I'd suggest spending at least £12.50 not including delivery charges just to be on the safe side.
In my experience Quidco bonuses usually come through automatically a day or two after the purchase cashback reaches 'payable', but if that doesn't happen then their support team is pretty good for applying it manually if you contact them.
Participation is by eligible account holders making a cashback qualifying purchase and opting in via email link or link on homepage, http://www.quidco.com/incentives/incentive-sept-ten-la.
A qualifying purchase requires the member to opt in and make a cashback earning purchase through the Quidco site before midnight 30 September 2016.
The £10 bonus will be automatically added to users' accounts 3 days after the purchase has been confirmed by the retailer.
In order to qualify for the bonus the member must spend a minimum of £10 plus VAT and delivery at a retailer that offers cashback. Any transactions where no spend is required will not qualify for the bonus.