Santander has been fined £107.8m implicit "serious and persistent gaps" successful its anti-money laundering controls which opened the doorway to "financial crime".
The fiscal watchdog said the slope "failed to decently oversee and manage" systems aimed astatine verifying accusation provided by concern customers.
Santander besides failed to decently show the wealth customers had going done their accounts.
The slope said it was "very sorry" for the failings and had taken action.
Mark Steward, enforcement manager of enforcement and marketplace oversight astatine the Financial Conduct Authority (FCA), said: "Santander's mediocre absorption of their anti-money laundering systems and their inadequate attempts to code the problems created a prolonged and terrible hazard of wealth laundering and fiscal crime.
The failings affected the oversight of accounts held by much than 560,000 concern customers betwixt 31 December 2012 and 18 October 2017, and led to much than £298m passing done the slope earlier it closed accounts.
The FCA said that successful 1 case, a caller lawsuit opened an relationship arsenic a tiny translations concern with expected monthly deposits of £5,000. Within six months it was receiving millions successful deposits, and swiftly transferring the wealth to abstracted accounts.
Although the relationship was recommended for closure by the bank's ain anti-money laundering squad successful March 2014, the FCA said that mediocre processes by Santander meant that it was not acted upon until September 2015.
As a result, the lawsuit continued to person and transportation millions of pounds done its account.
The City watchdog identified respective different concern banking accounts which Santander failed to negociate correctly, leaving the slope unfastened to "serious wealth laundering risk".
Santander main enforcement Mike Regnier said: "We are precise atrocious for the humanities anti-money laundering related controls issues successful our Business Banking part betwixt 2012-17 highlighted successful the FCA's findings."
He said the slope took enactment to code the issues erstwhile they were identified, but accepted that its anti-money laundering controls astatine the clip should person been stronger.
"We person since made important changes to code this by overhauling our fiscal transgression technology, systems and processes, helium said, adding that much than 4,400 Santander unit are present focused connected preventing fiscal crime.