Guidance

Annex E: Error Reduction Strategy 2026

Updated 12 October 2026

This updates the previous Annex E published in the code of practice 2025.

National Error Reduction Strategy 2026: to be fully implemented by 2 November 2026.

The purpose of this strategy is to reduce the risk of errors in the acquisition, handling and use of communications data by setting out clear checks, responsibilities and safeguards for investigators, SPoCs, supervisors and authorising individuals. It supports accurate decision-making, effective oversight and the prevention of harm arising from incorrect data. SPoCs are reminded that under paragraph 5.22 of the CoP they are responsible for assuring that Part 3 authorisations are lawful under the Act and free from errors.

This latest release of the ERS replaces all pre-existing versions and is correct at time of going to press. CDS and GOV.UK will host the most up to date version.

In the event of proceedings before the Investigatory Powers Tribunal or similar, account may be taken of the extent of compliance with this guidance.

Who	Application or process	Action or responsibility
SRO	Compliance	The SRO is responsible for the compliance with any error reduction procedures that have been set and agreed by the Home Office and the Investigatory Powers Commissioner – CoP Para 4.10.
Investigator / SPoC	IPAR	Enforcement action based on the result of a single IPAR should be a last resort. Every opportunity should be taken to resolve other associated identifiers within the source document i.e. other IP activity or verified email addresses / mobile phone numbers.
Investigator / SPoC	IPAR	Recognise the particular difficulties of single strand information where enquiries will be dealt with ‘out of hours’ – unless there is an immediate need to prevent death, serious injury, or any damage to a person’s physical or mental health such enquiries should be dealt with during normal working hours.
Investigator / SPoC	Oral process	Recognise the enhanced risk of errors whenever the urgent oral process is used. Risks include the verbal passing of identifiers, lack of corroboration and latency of data reaching the event data record.
Investigator	Verify data	Upon the receipt of any information an immediate check for errors should take place. In the case of CSE/A referrals this will be material downloaded from source systems.
Investigator / SPoC / SRO	All internet-based applications	Where possible, a source or supporting document containing the details to be acquired or resolved must be attached to the application. A recognised source is one whose provenance and reliability can be established by the applicant and SPoC. Where no source or supporting document exists, the investigator must state this in the application and explain why it is unavailable. All IPAR applications must then undergo Peer Review (1). For other internet-based applications, a SPoC must compare the application data line with the accompanying source or supporting document.
Investigator / SPoC	All internet-based applications	Investigator and SPoC will check, verify, and agree date format – UK dd/mm/yyyy v US mm/dd/yyyy.
Investigator / SPoC	Time Selection	Avoid requesting data either around midnight, or at the end of a calendar month. These are easy ways to avoid common causes of error.
Investigator	Data input	Where possible all relevant identifiers alongside dates / times should all be copy / pasted (CTRL+C / CTRL+V) into an application. Confirming the method of transposition into the application is advised. If not possible, a second person must verify these details have been inputted correctly with the application suitably endorsed.
Investigator / SPoC	IPAR	Where available lease times for the allocated IP should be sought.
Investigator / SPoC	IPAR	Agree the most appropriate IP addresses to resolve where they have been acquired from an IP History result, to mitigate risk of transposition or TO errors. Where both fixed line and resolvable mobile IPs are available, both should be resolved to increase the opportunity to focus on the appropriate subject. Great care should be taken if the IP activity being resolved is within 24hrs of the start or end time of the relevant session.
Investigator	IPAR	Multiple IP addresses should be grouped by relevant TO.
SPoCs	IPAR	Peer Review (1) A second SPoC (or subject to SRO and the IPC’s approval, another agreed person) must check the accuracy of the CD being sought against the source or supporting document. This review must endorse as accurate the following prior to submission to IPCO: • all identifiers’ dates and times • any time zone adjustments
SRO / SPoC	Compliance	Identifying an inaccuracy during Peer Review (1) or Peer Review (2) prevents a relevant error. Near misses must also be recorded and reviewed internally so that learning can be identified and shared.
IPCO Authorisations	All internet-based applications	Authorising Individuals shall return all applications if the following is missing or not explained: • For IPAR: no confirmation of Peer Review (1) being carried out. • Where the application seeks the resolution of a single IP address. • For all other internet data requests E.g. usernames, email / MAC addresses: no confirmation that a SPoC has checked the application data line against the accompanying document.
SPoCs	IPAR	Peer Review (2) — where the process allows an independent check before service Where the acquisition process provides sufficient time and access for an independent check before the request is sent or served, a second SPoC must verify that all submitted identifiers, dates, times and time zones have been entered accurately on the TO portal or notice. The SPoC must record when Peer Review (2) cannot be completed and the reason.
SPoC	Automated Acquisition	Where CD is acquired through AA, Peer Review (2) is not possible; Peer Review (1) is therefore particularly important.
SPoCs	IPAR	Peer Review (3) A check is made before release to verify that the identifiers in the returned result match those contained in the application and source / supporting document.
SPoC	Automated Acquisition	Recognise that when AA is used, the applicant may receive the result at the same time as the SPoC. Immediate contact by the SPoC to the applicant is vital if the SPoC Peer Review (3) identifies an error.
Supervisor	Enforcement Action	A package for the consideration of enforcement action must be reviewed by a supervisor for accuracy and suitable corroboration. No executive action should be taken without adequate corroboration. This may be the last opportunity for potential errors to be identified before operational activity.
Investigator	Enforcement Action	Any package forwarded to another organisation must include the source or supporting document and the original CD application form, where available. The investigator must provide a document schedule identifying each item supplied. If a source, supporting document or application form does not exist or is unavailable, the package must state this and explain why.
Investigator	Enforcement Action	Before considering action, the receiving LEA must check the package against the document schedule and confirm that every listed item has been received and reviewed. Where the schedule records that a document does not exist or is unavailable, the receiving LEA must review the explanation and decide whether the available material is sufficient to proceed. Involvement of a SPoC in this checking process is at the discretion of the SRO.
Investigator / SPoC	Unexpected Results	Investigators must feedback to SPoCs any unexpected results. Each can be an indicator of a relevant error (unconnected persons) or incorrect submission (no data when data was expected). In turn, unexpected results from a TO must be discussed with KET to decide who is best placed to raise the issue with the TO (UK or Overseas).
Investigator / SPoC	Liaison	Appreciating the difficulty where online investigation units are not co-located, it is important to ensure constant contact between investigators and SPoCs.
Investigator / SPoC	Use of CD Services database	Changes to CD services alongside IPCO’s findings from error investigations can lead to publications upon CDS of the issue and measures to prevent a reoccurrence. These can be found by typing ERS into the search box. Awareness of these bulletins by all involved in the acquisition process is essential.

The 2026 National Error Reduction Strategy differs from the 2025 version in the following ways:

• It moves from a primary focus on IPAR to all internet-based communications data applications. It requires source or supporting evidence to be attached where available; where none exists, the investigator must record and explain its absence. It also requires non-IPAR application data to be checked against the supporting material.

• Peer reviews must be conducted by SPoCs unless the SRO has agreed an alternative arrangement with the IPC.

• It strengthens information-sharing processes, requiring the receiving organisation to be provided with the source / supporting document and the original communications data application form (where available).

Acronyms

AA

Automated Acquisition

CD

Communications Data

CDS

Communications Data Service

CoP

Code of Practice

CSE/A

Child Sexual Exploitation / Abuse

ERS

Error Reduction Strategy

HO

Home Office

IPC

Investigatory Powers Commissioner

IPCO

Investigatory Powers Commissioner’s Office

IP

Internet Protocol

IPAR

IP Address Resolution

IPT

Investigatory Powers Tribunal

KET

Knowledge Engagement Team

LEA

Law Enforcement Agency

MAC

Media Access Control

NCMEC

National Center for Missing and Exploited Children

SRO

Senior Responsible Officer

SPoC

Single Point of Contact

TO

Telecommunications Operator