Wise (NASDAQ: WSE), the payments company that has branched into savings and investment products, has identified a multi-year flaw in tax paperwork sent to roughly four thousand of its UK based customers. The problem affected users of its Wise Assets offering, specifically the interest and stocks features, and covered statements issued from 2021 through 2025.
Figures for capital gains and investment income were miscalculated by software supplied by an outside vendor, so some account holders received numbers that were too high while others received numbers that were too low.
The discrepancy came to light through Wise’s own internal quality checks rather than through a customer complaint or a regulator inquiry.
Once the company confirmed the scope, it contacted the affected users and began discussions with HM Revenue & Customs about a collective arrangement.
Under the approach being explored, Wise would cover any tax shortfalls that arose because customers understated their gains or income on self-assessment returns.
At the same time, the firm has said it will repay anyone who overpaid because of the inflated figures.
Corrected statements have already gone out, and Wise states that the underlying software defect has been repaired, leaving no continuing exposure for clients.
Receiving an inaccurate statement does not automatically mean a customer filed an incorrect return or paid the wrong amount of tax.
Wise miscalculated tax for about 4,000 UK investment customers over four years and is seeking a bulk deal with HMRC to settle it.
The FT reports that third-party software used for Wise Assets got capital gains and income figures wrong between 2021 and 2025, so some customers… pic.twitter.com/DIWWCoYBQW
— Max Karpis (@maxkarpis) October 8, 2026
Personal circumstances, other income sources, and available allowances can all change the final liability, so the practical impact varies from person to person.
For those who do need to amend earlier filings, the bulk settlement under discussion with the tax authority could reduce the need for individual negotiations and speed up resolution.
The episode highlights a recurring operational tension for payments firms that have added investment functionality.
Accurate year-end tax reporting is a basic expectation in the UK market, yet many platforms rely on third-party tools to generate the capital-gains and income data that customers then copy into their returns.
When those tools fail, the platform still bears the customer-relationship and compliance consequences even if the code belonged to a supplier.
Wise’s decision to surface the issue itself, issue revised documents, and absorb both underpayments and overpayments may contain the immediate fallout, but it also shows how much remediation cost and administrative effort can attach to a vendor error that persisted across four tax years.
Customers who received the notification are now in a position to compare the new statements against what they previously declared.
Where differences are material, professional tax advice may be warranted before any amended return is submitted.
HMRC’s response to the proposed collective deal will determine how smoothly the remaining cases are closed.
In the wider fintech sector, the incident is likely to prompt closer scrutiny of the controls that surround outsourced tax-calculation engines, particularly as more firms layer brokerage and interest products onto core money-movement services.
Fintech firm Wise has stressed that the matter is limited in scale relative to its overall customer base and that remediation is already under way. The combination of self-detection, corrected paperwork, and a willingness to fund shortfalls offers a relatively orderly path out of the error, provided the settlement talks with the tax authority conclude without prolonged dispute.