The NAAB, the two referral routes, and what local authorities need to know before they choose

In my last piece I set out the legal architecture the Home Office's Facial Age Estimation tool must meet before it can be lawfully deployed. That piece was about a tool at the front end of the system. This one is about what happens further in, and what it means for the local authority that either refers a young person to the National Age Assessment Board, or finds itself in a dispute with the Home Office about whether to do so at all.

Two Upper Tribunal judgments have shifted the landscape in the past six months. But before turning to the case law, the procedural picture matters. How the NAAB becomes involved determines who is legally responsible, who can control the outcome, and who bears the consequences if the assessment is wrong.

The National Age Assessment Board was established under the Nationality and Borders Act 2022. It operates under two distinct statutory powers, and the distinction carries significant legal consequences.

Section 50 of the 2022 Act applies where a local authority refers a young person to the NAAB. The authority may do so because it genuinely needs the NAAB's expertise, for example where the case is particularly complex, or where internal capacity is stretched. That second reason is increasingly common.

The demand on local authorities is not a background feature of this landscape. It is the driving force behind why the NAAB is being used as frequently as it is.

Section 51 of the 2022 Act applies where the Home Office itself initiates the NAAB assessment. This happens in two circumstances: where the Home Office disputes the outcome of a local authority's age assessment, and where the Home Office disagrees with a local authority's decision not to conduct an age assessment at all, typically because the authority has accepted the young person's claimed age.

The Age Assessment Joint Working Guidance sets out an escalation procedure that applies before the Home Office can proceed to a section 51 referral. The guidance requires the dispute to be escalated to senior management on both sides, typically to the local authority's Head of Service or Director level, and to a senior Home Office decision-maker. If that escalation does not produce agreement, the Home Office proceeds to refer to the NAAB under section 51.

The two routes create different legal landscapes, and practitioners need to be clear about which one they are in.

When a local authority refers under section 50, the NAAB's determination is legally binding on the authority. This is not a consultative process. The authority is not retaining a decision it can revisit. It is transferring its decision-making function to the Home Office's own body.

The practical and legal consequences of that transfer are significant.

The consequences of that Interested Party status are sharply felt when interim relief is in play. If the court grants interim relief, ordering that the young person be treated as a child pending determination, that order will almost certainly be directed at the local authority, because it is the local authority that holds the Children Act 1989 duties. The SSHD does not have section 20 accommodation. The local authority does.

There is a further consequence that some authorities do not fully anticipate at the point of referral: if the NAAB decides to concede the judicial review proceedings, accepting that its assessment was wrong, it is the Home Office that makes that decision. The local authority cannot control whether the case is settled or defended. But the local authority will have to accommodate and support the young person regardless. If the NAAB concedes, the practical and financial consequence lands with the authority that made the original section 50 referral.

This is not a reason never to use the NAAB. In many cases, it is the right decision. But it is a reason to take the referral decision with full knowledge of what is being handed over.

A section 51 referral arises from disagreement. The Home Office does not accept the local authority's assessment, either because the authority has assessed the young person as a child and the Home Office disagrees, or because the authority has accepted the young person's claimed age without a formal assessment.

The Age Assessment Joint Working Guidance requires escalation before this referral is made. In practice, this means a local authority team manager or Head of Service receiving a communication from a Home Office senior caseworker indicating that the Home Office disputes the authority's assessment and is proposing to refer to the NAAB. That communication should trigger an immediate escalation process, documented in writing, before any NAAB referral is made.

A section 51 NAAB assessment is, legally, not binding on the local authority in the same way as a section 50 assessment. It constitutes 'new information' that the authority must take into account, but it does not automatically displace the authority's own Merton-compliant determination. The authority can maintain its position that the young person is a child and continue to provide Children Act services accordingly.

That said, the dual-age situation will not persist indefinitely. It will generate litigation. And when it does, the correct defendant is again the Secretary of State, not the local authority. The challenged decision is the NAAB assessment, an exercise of the Home Office's section 51 power. The local authority will be joined as an Interested Party. And, as in Route 1, any interim relief order is likely to be directed at the authority.

The fact that the correct defendant is the SSHD, not the local authority, has consequences beyond who pays the court fees. It means the local authority is not the decision-maker in the litigation. It cannot unilaterally settle. It cannot decide to concede the factual issue. It cannot amend the grounds. Those decisions belong to the Home Office and its legal team.

What the local authority can do is exercise its right as an Interested Party to engage actively with the proceedings, particularly on interim relief. If the Home Office's legal position is that the young person should be treated as an adult pending determination, and the local authority's own Merton assessment places the young person as a child, the authority's active participation can be dispositive at the interim stage.

Local authority legal teams should not treat Interested Party status in NAAB cases as a watching brief. It is an opportunity, and in the context of interim relief, where the order will fall on the authority, it is effectively a necessity.

In R (SS) v SSHD [2025], the Upper Tribunal quashed one of the first NAAB age assessments to be challenged before it. The facts are set out in detail in the earlier version of this article and remain important. SS was an Afghan young person with untreated epilepsy, PTSD, and below-average cognitive functioning. He said 'I don't know' 158 times during the NAAB assessment. The NAAB read that as deliberate evasion. Three medical experts explained it as a symptom of his conditions. The Tribunal found the assessment was wrong. SS was a child. He had been rendered homeless and was being processed through the Youth Court as an adult.

The NAAB assessment in SS was a section 50 referral, made by Croydon. The NAAB conceded late in the proceedings. Croydon, as Interested Party and the holder of Children Act duties, bore the immediate consequence.

In R (NXP and NAN) v SSHD [2026], the Upper Tribunal confirmed that challenges to NAAB assessments belong in the Upper Tribunal, not the High Court. That procedural clarification matters for practitioners: it sets the forum and confirms the respondent.

Together, the two cases establish: NAAB assessments will be scrutinised on their factual merits; no special institutional deference is afforded to the NAAB; and the UT is willing to make its own findings on age where the evidence supports it.

If your authority is in a section 51 dispute with the Home Office, the HO is challenging your assessment or your decision not to assess, the escalation procedure is your first and most important tool.

If the young person's clinical presentation raises any doubt about cognition, mental health, or the effects of trauma, and for UASC it almost always should, a referral for psychological or medical assessment should be made before the escalation process concludes. R (SS) demonstrates what happens when medical evidence is absent at the assessment stage and only arrives at the litigation stage: the correct answer is found, but the damage done in the interim is severe.

Record-keeping is the foundation. The Merton-compliant assessment must show holistic, welfare-led reasoning. The escalation correspondence must show a clear professional position maintained under pressure. The clinical referral must show that the authority took seriously the alternative explanations for the young person's presentation. If any of those elements are missing, the authority's position, whether as respondent, interested party, or the body holding interim relief obligations, is weakened before the litigation even begins.

If your authority is at that point now, a live Home Office dispute, a NAAB referral signalled, or an existing NAAB assessment under challenge, this is the moment to review your position, your recording, and your legal team's instructions.