Investment Security Unit (United Kingdom)

The Investment Security Unit (ISU) administers the United Kingdom's National Security and Investment (NSI) screening regime. It receives notifications, supports assessments and monitors aspects of compliance. The unit is not itself the statutory decision-maker for every call-in, condition or prohibition.

Statutory framework

The National Security and Investment Act 2021 gives the government powers to review acquisitions that may create national-security risks. The Notifiable Acquisition Regulations define 17 sensitive sectors for mandatory notification, subject to the current definitions and amendments. Acquisitions outside those rules may still be notified voluntarily or called in where the statutory test is met.

The process separates mandatory and voluntary notifications, acceptance, call-in, assessment, final notification and final order. A final notification clears the matter without conditions under the regime. A final order can impose conditions, prohibit an acquisition or require remedies within statutory powers. Parties retain review rights.

Institutional boundary

The ISU performs the administrative work and serves as the contact point for businesses. The competent minister or designated decision-maker exercises statutory powers. Intelligence bodies, sector departments and advisers may inform an assessment, while courts provide judicial review.

The ISU transferred from the former Department for Business, Energy and Industrial Strategy to the Cabinet Office in February 2023. Its departmental home and ministerial allocation remain subject to machinery-of-government change and require a publication-day check. Referring to an ISU decision can therefore obscure the legal actor responsible for the outcome.

Orders, evidence and limits

The 2022 final order concerning Nexperia's acquisition of Newport Wafer Fab illustrates the power to require divestment. The public notice states the reasons the government chose to disclose. It does not support unstated inferences about wrongdoing, hostile direction or an entire nationality or sector.

Annual reports provide notification volumes, call-ins, outcomes and processing data for defined periods. Screening effectiveness and deterrence cannot be inferred from those counts alone. Redacted or terse orders leave some reasoning unknown.

Statecraft significance

The ISU belongs in the main sequence because ownership screening can deny control over strategic assets, impose risk-mitigation conditions and strengthen resilience. The mechanism is defensive economic statecraft exercised through investment law.

Each case requires the statutory stage, decision-maker, public reasons, remedy and review status. A notification or call-in is not a finding of misconduct. Current sector definitions, guidance, final orders and judicial outcomes must be refreshed before publication.

See also

Committee on Foreign Investment in the United States (CFIUS) · Foreign Investment Review Board (Australia) · EU FDI Screening Regulation (2019/452) · Critical-infrastructure ownership review · Strategic corporate acquisition · Golden shares and special state control rights

Sources

• United Kingdom Parliament, 'National Security and Investment Act 2021', current text checked 29 July 2026.
• United Kingdom Government, 'National Security and Investment Act 2021 (Notifiable Acquisition) Regulations 2021', with current amendments checked 29 July 2026.
• Cabinet Office, 'National Security and Investment Act Guidance on Acquisitions', checked 29 July 2026.
• Cabinet Office, National Security and Investment Act Annual Report 2024 to 2025 (22 July 2025).
• Department for Business, Energy and Industrial Strategy, 'Acquisition of Newport Wafer Fab by Nexperia BV: Notice of Final Order' (16 November 2022).
• Rory Phillips and Georgina Wolfe, 'Intervention in Investments on National Security Grounds', in National Security Law, Procedure and Practice (Oxford University Press, 2024), 489-512.
• Cabinet Office, 'Operation of the National Security and Investment Act 2021: Memorandum of Understanding between the Cabinet Office and the CMA' (26 March 2026), confirming the February 2023 transfer of the ISU.