Right now at Debenhams if you spend £40 or more online you can get a free £5 gift card.
It seems like a pretty straightforward deal. If you make a purchase online or in-store of £40 or more between Sunday 22nd February and Sunday 15th March 2015, you'll qualify for a £5 promotional gift card.
If your purchase is in-store, you'll be given your gift card in person (while stocks last) and if you make a £40 purchase online, your free £5 gift card will be emailed to you between Monday 16th and Friday 20th March 2015.
You can only claim one gift card per customer per day, so even if you spend £40 twice in two separate transactions on the same day, you'll only get one gift card.
Do note, too that you can't claim your free gift card if you're redeeming any kind or promotional voucher, and if you subsequently return your purchases then Debenhams say they reserve the right to request the promotional gift card back, or reduce the value of your refund by £5.