Thousands of Kiwis have been affected by a Lotto IT problem which meant more money was withdrawn from their accounts than expected. 

Lotto confirmed in a statement that leading up to Wednesday's draw, around 25,000 customers who were trying to top up their accounts were impacted. 

They said the issue occurred from just before 7pm until 7.30pm on Wednesday night and happened because their payment partners experienced delays with their card processing systems. 

"This was exacerbated by the very heavy traffic on the MyLotto platform leading up to the draw. As you will know, the Powerball jackpot was $42 million on Wednesday, and as a result we sold three times as many tickets to that draw as we would sell on an average Wednesday night draw. Many customers came online at the last minute to purchase a ticket." 

Cherry Milward, who received a refund this morning, was one of the affected customers. 

Milward said she and her husband decided to each put $50 into their separate Lotto accounts from their joint bank account. 

Unfortunately, she said after trying once it wouldn't work, and they were both unable to load money on their accounts. 

When she checked her bank account a few hours later she was shocked to discover $260 was pending in different payments to come out of their joint bank account. 

She called Lotto and said a support person told her over the phone that they were having IT problems and that it had affected people all over the country. 

"[They said] within 24 hours the pending will be taken off and your bank account will be back to normal, and I was like oh it's a bit irritating but it's fine." 

However on Friday, Milward said the money had been taken out of her bank account, and only $50 of the $260 had actually gone into her Lotto account. 

"Some people probably are oblivious that it's even happened, like older people, online banking and all the rest of it. 

"I think publicly acknowledging they've screwed up would be good." 

Lotto said the issue meant some customers attempted to top-up their MyLotto wallets multiple times because they did not see the funds appear after the first attempt. 

"Around 25,000 customers were affected (approximately 4 per cent of the total who purchased tickets for the draw). For the majority of these customers, the total amount they transferred to their MyLotto wallet (across multiple transactions) was less than $50, but for some – like the customer you have spoken to – it was more than that." 

The statement said they identified the problem and on Thursday processed refunds for affected customers. 

"Many customers have already had the funds credited back to their accounts, but the time it takes will depend on the time it takes for their bank to process the transaction. We also sent every affected customer an email on Friday morning, explaining what had happened and letting them know what we were doing to resolve it." 

The company told the Herald they sincerely apologise to affected customers and understand the concern the issue had caused.