The WannaCry cyberattack in May cost one NHS trust £9.5m in lost income, its latest board report reveals.
The international incident affected business and government computer systems across the world.
In the NHS, the highest profile disruption was at Barts Health Trust, which was forced to cancel dozens of procedures, many for specialist work.
A report to the trust’s board this month said the attack by the virus, known by various names including Wanna Decryptor, cost the organisation £9.5m in lost income this financial year.
A spokesman for the trust said a further £4.8m of income was lost or spent on “bringing in digital experts to help recover from the cyber disruption.”
Another report said a safety review into the incident was carried out and no patients had come to harm.
The number of NHS organisations affected by the attack rose rapidly from 26 on 12 May to 50 later in the week.
NHS Improvement chief executive Jim Mackey said at the time: “The effect on different organisations is variable, while issues around causes and coordination remain unclear.”
Later, Mr Mackey told an NHS Improvement board meeting the response from national bodies had been less than ideal.
At the end of quarter two, Barts had a deficit of £88.5m, £35.9m worse than planned.
HSJ asked the trust what comprises the other £26m of the downturn but it had not responded by the time of publication. Fines over non-delivery of emergency access times targets accounted for £3.2m.
A trust finance report said: “The trust continues to work to mitigate this risk and to recover lost activity as quickly as possible in the most cost efficient manner.”
The £1.1bn turnover trust us predicting a full-year deficit of £65m in 2017-18.
Trust board papers