Morrisons is struggling to deliver some orders for Christmas after problems with its loyalty card and its click-and-collect service.
Price discounts on its More Card weren’t being registered said customers, while others had been told that some deliveries might arrive late.
Morrisons, which has been heavily discounting its Christmas ranges, told the BBC: "All our stores have now made the top 100 More Card prices the regular price - including the 10p veg deal, turkeys, spirits and champagne.
"In addition, we will give More Card customers an extra 10% off their entire shop as an apology."
Morrisons has been showing signs of recovery under new chief executive Rami Baitieh after taking on a pile of debt when it was acquired by US private equity fund CDR.
"There's never a good time for a tech glitch, but for it to happen on what is expected to be the busiest day of the year is the stuff of nightmares," retail analyst Natalie Berg. Told the BBC.
"This will further erode shopper trust and impact profitability.
Morrisons is the fifth-largest market supermarket in the UK, according to Kantar, with 8.6% of the grocery market in the 12 weeks leading up to 1 December 2024.
Grocery sales this Christmas are expected to hit a record of more than £13 billion according to market research group Kantar.
Tesco PLC (LSE:TSCO)shares were up slightly while Sainsbury's eased 0.4%.