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Fujitsu supplied and supported Horizon, the Post Office branch-accounting system whose bugs, data limitations and remote-access capabilities helped turn unexplained shortfalls into allegations of theft. The Post Office—not Fujitsu—decided to investigate, sue and prosecute postmasters, but Fujitsu’s technical evidence and disclosures were central to the cases. As of 18 August 2026, Fujitsu had apologised and funded restorative justice, while its quantified contribution to compensation remained unresolved.
The short version
- Fujitsu developed, supplied and maintained Horizon for Post Office branches.
- Horizon could produce incorrect balances through software bugs, reconciliation failures and other defects. A displayed shortfall was not automatically proof that a postmaster had stolen money.
- Fujitsu had remote-access capabilities. Inquiry evidence says staff could alter branch data without a postmaster’s knowledge and, in some extracts, insert transactions that appeared to be ordinary branch transactions.
- Fujitsu staff knew about system problems years before the scandal became public. Parliamentary evidence discussed defect work dating from 2001–04 and a 2006 contract addressing Horizon errors.
- The Post Office used Horizon figures and Fujitsu-generated technical material in disciplinary, civil and criminal cases. It was the prosecuting organisation.
- Fujitsu has accepted moral responsibility and apologised. Its eventual civil, contractual or other financial liability is not finally determined.
The statutory inquiry’s published Volume 1 focuses on human impact and redress; it is not the final answer to every technical, contractual or evidential question about Fujitsu. See the Post Office Horizon IT Inquiry and its reports and statements.
What Horizon was
Horizon was the Post Office’s electronic point-of-sale and branch-accounting system. Fujitsu, following the earlier ICL corporate history, developed and supplied it and provided maintenance and support under its contractual arrangements.
The problem was not one isolated “glitch”. The evidence concerns software bugs, coding and reconciliation errors, defective handling of data, inadequate explanations of discrepancies and an institutional assumption that computer output was inherently reliable. Parliament’s discussion of Fujitsu’s role is set out in its report at committees.parliament.uk/publications/52110/documents/290159/default/.
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How an apparent shortfall became an accusation
- Horizon displayed an apparent discrepancy in a branch account.
- The postmaster was generally expected to make good the amount or explain it.
- If the difference remained unresolved, the Post Office could suspend the postmaster, terminate the contract, demand repayment, bring civil proceedings or refer the matter for prosecution.
- Horizon data and technical statements were used to present the discrepancy as a branch-level accounting failure.
- Complaints that the system was wrong were often treated as excuses rather than as evidence requiring investigation.
Some individual discrepancies may have been genuine accounting mistakes; others were caused or contributed to by Horizon errors, data problems or interventions. The existence of bugs does not prove the cause of every shortfall. It does, however, undermine the Post Office’s broad assumption that an unexplained computer figure established dishonesty.
What Fujitsu actually did
Developer, supplier and defect manager
Fujitsu designed and supplied Horizon, maintained the system, investigated faults and worked on corrections and reconciliation processes. A contract described in January 2026 parliamentary evidence, dated August 2006, dealt with fixing Horizon defects and liability for losses caused by system errors.
Technical support provider
Fujitsu personnel supported the Post Office when branches reported problems. Inquiry material refers to staff working on wrong-payment issues as early as 2001–04, including a substantial team addressing those problems. This supports knowledge that defects existed; it does not by itself prove that Fujitsu caused every later loss.
Provider of data and expert evidence
Fujitsu supplied data extracts, explanations and witness material used in disputes and prosecutions. The reliability, completeness and wording of that material therefore mattered as much as the underlying code.
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Remote access was an operational capability, not automatically a cyberattack. Depending on the function, it could mean viewing data, running diagnostics, applying an authorised correction or changing records remotely. The serious issue was that inquiry evidence says Fujitsu could alter branch data without the postmaster’s knowledge. Other material says Fujitsu-inserted transactions could appear indistinguishable from ordinary branch transactions in certain extracts.
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Why remote access mattered
A branch ledger is persuasive evidence only if investigators know who could change it and can identify those changes. If a transaction inserted by a support employee appears as an ordinary branch entry, an extracted report may falsely suggest that the postmaster entered it. That possibility affected the evidential weight of Horizon records and the fairness of prosecutions.
The evidence does not establish that Fujitsu staff routinely fabricated every shortfall or that every loss was remotely created. The defensible conclusion is narrower: alteration was possible, relevant to the reliability of Horizon evidence and not adequately disclosed in the cases examined by the inquiry.
Key inquiry documents are SUBS0000028 and SUBS0000027; parliamentary oral evidence is at committees.parliament.uk/oralevidence/16966/html/.
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| Period | What the evidence indicates |
|---|---|
| 2001–04 | Fujitsu staff were accessing Horizon systems and working on wrong-payment problems, according to evidence cited to Parliament. |
| August 2006 | A contract addressed known Horizon defects and losses caused by system errors. |
| Before 2010 | Technical problems and support activity continued; knowledge of bugs was not new when postmasters challenged Horizon. |
| 2019 | The Bates group litigation publicly challenged the assumption that unexplained Horizon shortfalls proved postmaster dishonesty. |
| 2024–26 | The public inquiry and Parliament examined remote access, witness statements, disclosure, Fujitsu’s apology and compensation. |
Fujitsu UK chief executive Paul Patterson accepted in parliamentary evidence that Horizon had bugs and errors and that remote access existed. That is different from accepting that every allegation, individual shortfall or prosecution was caused by Fujitsu intervention. See the transcript and PDF at committees.parliament.uk/oralevidence/16966/pdf/ and the inquiry document POL00000600.
How Fujitsu evidence entered prosecutions
The evidential chain was usually:
- Horizon recorded a discrepancy.
- The Post Office treated it as a branch transaction or accounting failure.
- Fujitsu data extracts, technical explanations or witness statements were used to support the system’s reliability.
- The postmaster had to disprove the figure or repay it.
- The Post Office pursued disciplinary, civil or criminal action if the dispute continued.
Inquiry material describes standard wording that presented extracted records as original branch transactions even though Fujitsu staff could insert transactions remotely. It says the wording appeared in hundreds of witness statements and did not properly disclose the limitation. The issue was not simply that a computer made an error; it was that incomplete technical information could make unsafe computer evidence look conclusive.
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The Criminal Cases Review Commission describes convictions for theft, fraud and dishonesty in which faulty IT systems played an important role, and calls the scandal the largest single series of wrongful convictions in UK legal history. Fujitsu helped supply the technical foundation, but it did not decide whom to prosecute.
Why the Post Office was also responsible
The Post Office controlled the relationship with postmasters, decided when to investigate, demanded repayment, brought civil claims and conducted or instructed prosecutions. It also had duties to investigate complaints and disclose information that could undermine its cases.
That distinction matters. Calling Fujitsu the sole cause wrongly transfers prosecutorial and disclosure responsibility. Conversely, describing Fujitsu as a passive software vendor ignores its defect knowledge, support role, remote access and technical evidence. The scandal is best understood as shared responsibility with distinct parts: defective or unreliable technology, poor remediation, misleading or incomplete evidence, institutional reliance on computer output and failed oversight.
What the courts and inquiry established
The Bates group litigation
The group litigation was a turning point because it challenged the Post Office’s assumption that unexplained Horizon losses necessarily resulted from postmaster dishonesty. It exposed serious weaknesses in the reliability of Horizon data, the handling of bugs and the Post Office’s approach to evidence. The litigation is part of the factual background, not a substitute for the continuing statutory inquiry. The inquiry’s primary materials are collected at postofficehorizoninquiry.org.uk/reports-and-statements.
Criminal appeals
Successful appeals and CCRC referrals showed that convictions could not safely rest on untested assumptions about Horizon. The number of investigated people, prosecutions, convictions, overturned convictions and compensation claimants is not the same; any headline total must define its population and date.
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The statutory inquiry
Volume 1 addresses human impact and redress. Technical, contractual, evidential and accountability questions continue through the inquiry record, government implementation and other investigations. It would be inaccurate to say that every question about Fujitsu has been finally resolved.
Fujitsu’s apology and financial position
Fujitsu publicly apologised for its role in the suffering of affected postmasters. An apology is evidence of moral responsibility, not automatically an admission of every allegation or a final finding of civil or criminal liability.
The restorative-justice funding is separate from compensation. The government’s programme update is at gov.uk/government/publications/post-office-horizon-it-inquiry-update-on-the-restorative-justice-programme. Fujitsu had therefore paid something connected with repair and apology, but had not agreed its final contribution to financial redress.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Compensation and redress schemes
There is no single “Post Office compensation scheme”. Different groups are covered by different arrangements:
- Overturned Convictions Scheme: for people whose convictions were quashed or otherwise meet the scheme’s criteria.
- Horizon Shortfall Scheme: for postmasters who suffered Horizon-related financial shortfalls but were not convicted.
- Group Litigation Order scheme: for claimants involved in the group litigation.
- Family-member redress: for close relatives who suffered personal injury, including mental injury, connected to the scandal. The government announced a new scheme at gov.uk/government/news/new-redress-scheme-announced-for-horizon-scandal-family-members; opening status should be checked in the current GOV.UK inquiry collection.
- Restorative justice: facilitated meetings, apologies and related measures, which are not a substitute for compensation.
Parliamentary material reported that, by March 2026, more than 11,300 claimants had received payments totalling £1.44 billion. Those figures are time-sensitive and should not be treated as a final total. The March report is at committees.parliament.uk/committee/365/business-and-trade-committee/news/212661/post-office-horizon-it-scandal-serious-structural-failings-persist-in-redress/.
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How many people were affected?
The answer depends on the group counted: people investigated over shortfalls; contracts terminated; people prosecuted; convictions entered; convictions overturned; compensation claimants; or family members suffering consequential harm. No single number accurately describes all of them. The CCRC’s case summary at ccrc.gov.uk/post-office/ explains the criminal-case population, while redress totals cover wider groups.
Is Fujitsu still receiving government work?
This is a live procurement question, not one with a safe blanket answer. Parliamentary committees were examining Fujitsu’s inclusion on government procurement frameworks in July 2026. That correspondence is available at committees.parliament.uk/work/9524/post-office-horizon-scandal-justice-for-subpostmasters/publications/3/correspondence/. The documents should be checked for the precise framework and date; they do not justify saying Fujitsu is banned from all public contracts or that every restriction has ended.
What remains unresolved
- Fujitsu’s eventual quantified contribution to compensation.
- The final allocation of contractual, civil, regulatory and any criminal responsibility.
- Outstanding unsafe convictions and delayed or incomplete redress.
- How government procurement, expert evidence, disclosure and software assurance should change.
- The transition from Horizon and the preservation of evidence needed by claimants and investigators.
The strongest established account is therefore neither “Fujitsu alone caused everything” nor “the Post Office was merely misled by a vendor”. Fujitsu supplied a defective and highly consequential system, knew important problems existed and provided evidence whose limitations mattered. The Post Office chose to rely on that system, pursued postmasters and failed to deal properly with information undermining its cases. Final financial and legal accountability remains unfinished.
Frequently Asked Questions
Did Fujitsu invent every Horizon shortfall?
No. The evidence establishes bugs, data problems and the capability for remote alteration, but it does not prove that every individual shortfall was remotely created or caused by Fujitsu. Each case requires its own evidence.
Did Fujitsu prosecute postmasters?
No. The Post Office investigated, brought civil claims and prosecuted. Fujitsu supplied the system and technical evidence on which the Post Office relied.
Could Fujitsu change Horizon data remotely?
Inquiry evidence says Fujitsu had the ability to alter branch data without a postmaster’s knowledge, and that some inserted transactions could appear as ordinary branch transactions in extracted data. That capability did not mean every shortfall was altered remotely.
Has Fujitsu paid compensation?
As of 18 August 2026, Fujitsu had funded restorative justice but had not agreed a quantified contribution or timetable to the main compensation bill.
Is the Horizon inquiry finished?
Volume 1 has been published and addresses human impact and redress, but technical, contractual, evidential and implementation questions have not all been finally resolved.
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