Between October 2016 and July 2021, Nationwide had ineffective systems for keeping up-to-date due diligence and risk assessments for all its personal current account customers and for monitoring their transactions, the regulator found.

Nationwide was also aware that some of those customers were using their personal accounts for business activity, in breach of its terms.

In one serious case, Nationwide missed opportunities to identify a customer using personal current accounts to receive fraudulent Covid furlough payments.

The customer received 24 payments totalling £27.3m over 13 months, with £26.01m of this deposited over eight days.

HMRC recovered £26.5m, but approximately £800,000 is outstanding.

Nationwide did not offer business current accounts at this point, so did not have the right processes in place to manage the financial crime risks from business activity.

This meant Nationwide was unable to effectively identify, assess, monitor or manage the money laundering risks among its personal current account customers.

It also meant Nationwide did not have an accurate picture of its customers who presented a higher risk of financial crime.

FCA joint executive director of enforcement and market oversight Therese Chambers says: “Nationwide failed to get a proper grip of the financial crime risks lurking within its customer base.

“It took too long to address its flawed systems and weak controls, meaning red flags were missed with serious consequences.

“Building societies and banks have a key role in the fight against financial crime.

“Firms must remain vigilant in this fight.

“Nationwide was aware of weaknesses in its systems and controls and undertook work to make improvements.

“However, it failed to adequately address those weaknesses in a timely manner.

“Nationwide subsequently commenced a large-scale financial crime transformation programme in July 2021.”

A spokesperson for Nationwide Building Society says: “Nationwide identified these issues, which relate to controls in place before July 2021, through its own reviews, and voluntarily brought them to the attention of the FCA.

“The Society cooperated fully with the FCA investigation, and we are sorry that our controls during the period fell below the high standards we expect.

“Since 2021, Nationwide has invested significantly in all aspects of its economic crime control framework in order to ensure our systems are robust.

“We do not believe that these controls issues caused financial loss to any of our customers and remain committed to preventing economic crime and protecting our customers and the wider UK economy from fraud.”