diff --git a/web/src/components/OpportunityDialog.tsx b/web/src/components/OpportunityDialog.tsx
index 78f36f3..a9d65d2 100644
--- a/web/src/components/OpportunityDialog.tsx
+++ b/web/src/components/OpportunityDialog.tsx
@@ -15,7 +15,7 @@ import { api } from '@/api/client';
 import { errorText } from '@/lib/errors';
 import { statusLabel } from '@/lib/filterOpportunities';
 import { formatDate, formatMoney } from '@/lib/format';
-import { noticeSite } from '@/lib/opportunities';
+import { noticeSite, uuidLabel } from '@/lib/opportunities';
 import type { Opportunity } from '@/types/Opportunities';
 import { ReleaseTabs } from './ReleaseTabs';
 import { buttonPrimary, statusBadge } from './styles';
@@ -134,7 +134,7 @@ export function OpportunityDialog(props: Props): JSX.Element {
                 <dd>{yesNo(opportunity().has_documents)}</dd>
                 <dt class="text-muted">Source</dt>
                 <dd>{opportunity().source}</dd>
-                <dt class="text-muted">OCID</dt>
+                <dt class="text-muted">{uuidLabel(opportunity())}</dt>
                 <dd class="break-all">{opportunity().uuid}</dd>
               </dl>
             </section>
diff --git a/web/src/lib/opportunities.test.ts b/web/src/lib/opportunities.test.ts
index b5efe80..88eeabb 100644
--- a/web/src/lib/opportunities.test.ts
+++ b/web/src/lib/opportunities.test.ts
@@ -7,6 +7,7 @@ import {
   latestRelease,
   mergeOpportunities,
   noticeSite,
+  uuidLabel,
 } from './opportunities';
 import { testOpportunity } from './testOpportunity';
 
@@ -96,3 +97,8 @@ test('a Find a Tender release’s page is its notice', () => {
     'https://www.find-tender.service.gov.uk/notice/095868-2026',
   );
 });
+
+test('an OCID is labelled as one, and other kinds of UUID as an ID', () => {
+  expect(uuidLabel(testOpportunity('ocds-h6vhtk-05a1b2'))).toBe('OCID');
+  expect(uuidLabel(testOpportunity('eusupply-uk-100114954', { uuid_type: 'eusupply' }))).toBe('ID');
+});
diff --git a/web/src/lib/opportunities.ts b/web/src/lib/opportunities.ts
index 648f1d4..496541c 100644
--- a/web/src/lib/opportunities.ts
+++ b/web/src/lib/opportunities.ts
@@ -83,3 +83,12 @@ const NOTICE_SITES: Record<string, NoticeSite> = {
 export function noticeSite(opportunity: Opportunity): NoticeSite | undefined {
   return NOTICE_SITES[opportunity.source];
 }
+
+/**
+ * What the opportunity's UUID is called on screen: "OCID" for an OCDS
+ * contracting process's id, and "ID" for the other kinds, such as
+ * eusupply-uk-<tender id>, which the app makes up itself.
+ */
+export function uuidLabel(opportunity: Opportunity): string {
+  return opportunity.uuid_type === 'ocid' ? 'OCID' : 'ID';
+}