diff --git a/src/utils/ownershipConsistency.test.ts b/src/utils/ownershipConsistency.test.ts
new file mode 100644
index 0000000..51cac67
--- /dev/null
+++ b/src/utils/ownershipConsistency.test.ts
@@ -0,0 +1,40 @@
+import { test } from 'node:test';
+import assert from 'node:assert/strict';
+import { checkOwnershipReadModelConsistency } from './ownershipConsistency';
+
+test('emits a structured error log when holder balances differ from stored supply', () => {
+   const events: Array<Record<string, unknown>> = [];
+
+   const mismatchDetected = checkOwnershipReadModelConsistency({
+      creatorId: 'creator-1',
+      storedSupply: 100,
+      holderBalances: [40, 20],
+      detectedAt: new Date('2026-01-01T00:00:00.000Z'),
+      logError: entry => events.push(entry),
+   });
+
+   assert.equal(mismatchDetected, true);
+   assert.equal(events.length, 1);
+   assert.deepEqual(events[0], {
+      creator_id: 'creator-1',
+      stored_supply: 100,
+      computed_holder_sum: 60,
+      discrepancy: -40,
+      detected_at: '2026-01-01T00:00:00.000Z',
+   });
+});
+
+test('does not emit a log when holder balances match stored supply', () => {
+   const events: Array<Record<string, unknown>> = [];
+
+   const mismatchDetected = checkOwnershipReadModelConsistency({
+      creatorId: 'creator-2',
+      storedSupply: 100,
+      holderBalances: [50, 50],
+      detectedAt: new Date('2026-01-02T00:00:00.000Z'),
+      logError: entry => events.push(entry),
+   });
+
+   assert.equal(mismatchDetected, false);
+   assert.equal(events.length, 0);
+});
diff --git a/src/utils/ownershipConsistency.ts b/src/utils/ownershipConsistency.ts
new file mode 100644
index 0000000..12659de
--- /dev/null
+++ b/src/utils/ownershipConsistency.ts
@@ -0,0 +1,32 @@
+export interface OwnershipConsistencyCheckParams {
+   creatorId: string;
+   storedSupply: number;
+   holderBalances: number[];
+   detectedAt: Date;
+   logError: (entry: Record<string, unknown>) => void;
+}
+
+export function checkOwnershipReadModelConsistency({
+   creatorId,
+   storedSupply,
+   holderBalances,
+   detectedAt,
+   logError,
+}: OwnershipConsistencyCheckParams): boolean {
+   const computedHolderSum = holderBalances.reduce((sum, balance) => sum + balance, 0);
+   const discrepancy = computedHolderSum - storedSupply;
+
+   if (discrepancy === 0) {
+      return false;
+   }
+
+   logError({
+      creator_id: creatorId,
+      stored_supply: storedSupply,
+      computed_holder_sum: computedHolderSum,
+      discrepancy,
+      detected_at: detectedAt.toISOString(),
+   });
+
+   return true;
+}