The energy firm reported itself to Ofgem, the energy regulator, after it discovered the incorrect charges last year.
Read on to find out what this means for Scottish Power customers and what to do if you think your energy provider is overcharging you.
Scottish Power overcharging
Around 1,699 direct debit customers were charged a higher rate (which should only have applied to standard credit customers) between 2015 and 2023.
Customers affected by this issue were overcharged an average of £149 over the eight year period.
Scottish Power says it took immediate steps to correct the issue when it was discovered last year.
It also said it's put in additional controls and monitoring in place to reduce the risk of anything similar happening in future.
Read more:How much compensation will customers get?
Scottish Power says it's refunded more than £250,000 to affected customers, alongside an additional £250,000 in goodwill payments.
On average, this equates to £294 per customer.
All payments will be made automatically, so you don't need to do anything if you were affected.
Scottish Power will also pay £1 million to the Energy Industry Voluntary Redress Fund, which helps vulnerable customers with energy-related support.
Which? director of policy and advocacy Rocio Concha said: 'With many households still struggling to afford their energy bills and the price cap significantly higher than it was before the energy crisis, suppliers need to ensure that billing is accurate and that customers are easily able to get in touch with customer service if something goes wrong.
'While many consumers will rightly consider switching, Scottish Power must urgently make improvements to ensure all customers are getting the service and support they need and deserve.'
Find out more:What to do if you’ve been overcharged
If you think your energy bills are incorrect, you can dispute them with your supplier.
Start by contacting your energy firm's customer service team outlining why you think you've been overcharged. Include evidence to support your case, including bills, photos of faulty meters or boilers, and records of previous correspondence.
Keep a copy of everything you send to your supplier, including energy bills, and note when you sent them. Make sure to also keep a written record of anything that's discussed over the phone.
If your energy provider refuses to acknowledge their misbilling, or doesn't give a decision within eight weeks of your complaint, you'll likely have reached a deadlock situation. This is when you've exhausted your energy company's complaints procedure without agreement.
Read more:source https://www.which.co.uk/news/article/scottish-power-to-pay-1.5m-in-refunds-and-compensation-for-overcharging-customers-ajVVE5S0EmWT