diff --git a/apps/edr-freight-api/src/modules/bookings/carriage-acceptance-price-split.spec.ts b/apps/edr-freight-api/src/modules/bookings/carriage-acceptance-price-split.spec.ts
new file mode 100644
index 000000000..195e0cab0
--- /dev/null
+++ b/apps/edr-freight-api/src/modules/bookings/carriage-acceptance-price-split.spec.ts
@@ -0,0 +1,26 @@
+import { BookingsService } from './bookings.service';
+
+// The split is a pure helper on the prototype (never touches `this`), so it can be
+// exercised without constructing the service and its dependency graph.
+const split = (total: number, weights: number[]): number[] =>
+  (
+    BookingsService.prototype as unknown as {
+      splitAmountAcrossWagons(total: number, weights: number[]): number[];
+    }
+  ).splitAmountAcrossWagons(total, weights);
+
+describe('carriage acceptance sheet — price split', () => {
+  it('splits proportionally to allocated weight', () => {
+    expect(split(100, [30, 10])).toEqual([75, 25]);
+  });
+
+  it('splits equally when no weights are recorded', () => {
+    expect(split(90, [0, 0, 0])).toEqual([30, 30, 30]);
+  });
+
+  it('always sums back to the booking total despite rounding', () => {
+    const shares = split(100, [1, 1, 1]);
+    expect(shares.reduce((a, b) => a + b, 0)).toBe(100);
+    expect(shares).toEqual([33.33, 33.33, 33.34]);
+  });
+});