Hi Steph,
It’s a reasonable question, there’s no need to appologise.
Matched betting is safe and legal and you don’t need to worry about declaring income. The legal system (in the UK) views matched betting as gambling. Its not taxable.
Although we know we’re doing the smart thing by utilising calculators and hedging bets, HMRC and the like view it as a gamble. Not to say there is no risk involved, you could make a mistake etc. However, there is nothing to worry about with income declaration or tax.
You’re just placing bets the smart way 🙂