With the Halifax Reward account pay in £1,000 per calendar month and you will receive a £5 Reward payment. For tax purposes please note that the £5 Reward payment is paid 'net' of income tax which means Halifax pay it after taking off income tax at the prevailing rate currently 20%. If you're a higher-rate taxpayer, you may have to pay extra income tax on the reward payment.
You may reclaim tax from HM Revenue & Customs if the amount of tax Halifax has taken off is more than you have to pay.