diff --git a/client/src/store/slices/budgetOrder.test.ts b/client/src/store/slices/budgetOrder.test.ts
new file mode 100644
index 000000000..29bf1427f
--- /dev/null
+++ b/client/src/store/slices/budgetOrder.test.ts
@@ -0,0 +1,30 @@
+import { describe, expect, it } from 'vitest';
+import type { BudgetItem } from '../../types';
+import { orderBudgetByCategories } from './budgetOrder';
+
+const item = (id: number, category: string | null): BudgetItem =>
+  ({ id, category, name: `item ${id}`, sort_order: id }) as unknown as BudgetItem;
+
+describe('orderBudgetByCategories', () => {
+  it('groups the items in the order the categories are given, keeping their order inside each', () => {
+    const items = [item(1, 'Food'), item(2, 'Hotel'), item(3, 'Food'), item(4, 'Hotel')];
+    expect(orderBudgetByCategories(items, ['Hotel', 'Food']).map((i) => i.id)).toEqual([2, 4, 1, 3]);
+  });
+
+  it('counts an item without a category as Other', () => {
+    const items = [item(1, null), item(2, 'Food'), item(3, '')];
+    expect(orderBudgetByCategories(items, ['Other', 'Food']).map((i) => i.id)).toEqual([1, 3, 2]);
+  });
+
+  it('puts the categories the list does not name last, in the order they were first seen', () => {
+    const items = [item(1, 'Fuel'), item(2, 'Food'), item(3, 'Tickets'), item(4, 'Fuel')];
+    expect(orderBudgetByCategories(items, ['Food']).map((i) => i.id)).toEqual([2, 1, 4, 3]);
+  });
+
+  it('ignores a named category no item has and leaves the items untouched', () => {
+    const items = [item(1, 'Food')];
+    const out = orderBudgetByCategories(items, ['Ghost', 'Food']);
+    expect(out).toEqual(items);
+    expect(out[0]).toBe(items[0]);
+  });
+});
diff --git a/client/src/store/slices/budgetOrder.ts b/client/src/store/slices/budgetOrder.ts
new file mode 100644
index 000000000..2c5d59000
--- /dev/null
+++ b/client/src/store/slices/budgetOrder.ts
@@ -0,0 +1,27 @@
+import type { BudgetItem } from '../../types';
+
+/**
+ * The budget items regrouped by category, in the order the categories are given.
+ *
+ * Items keep their order inside a category, an item without one counts as
+ * 'Other', and a category the list does not name follows the named ones in the
+ * order it was first seen. Shared by the local reorder and the reorder another
+ * member's client broadcasts, so both land on the same list.
+ */
+export function orderBudgetByCategories(items: BudgetItem[], orderedCategories: string[]): BudgetItem[] {
+  const grouped = new Map<string, BudgetItem[]>();
+  for (const item of items) {
+    const cat = item.category || 'Other';
+    if (!grouped.has(cat)) grouped.set(cat, []);
+    grouped.get(cat)!.push(item);
+  }
+  const reordered: BudgetItem[] = [];
+  for (const cat of orderedCategories) {
+    const inCategory = grouped.get(cat);
+    if (inCategory) reordered.push(...inCategory);
+  }
+  for (const [cat, inCategory] of grouped) {
+    if (!orderedCategories.includes(cat)) reordered.push(...inCategory);
+  }
+  return reordered;
+}
diff --git a/client/src/store/slices/budgetSlice.ts b/client/src/store/slices/budgetSlice.ts
index d1a9e8f66..054483a4d 100644
--- a/client/src/store/slices/budgetSlice.ts
+++ b/client/src/store/slices/budgetSlice.ts
@@ -7,6 +7,7 @@ import type { BudgetCreateItemRequest, BudgetFallbackFx, BudgetFreezeRatesRespon
 import { getApiErrorMessage } from '../../types'
 import { withFallbackFx } from '../../hooks/useExchangeRates'
 import { notify } from '../notify'
+import { orderBudgetByCategories } from './budgetOrder'
 
 type SetState = StoreApi<TripStoreState>['setState']
 type GetState = StoreApi<TripStoreState>['getState']
@@ -138,23 +139,7 @@ export const createBudgetSlice = (set: SetState, get: GetState): BudgetSlice =>
 
   reorderBudgetCategories: async (tripId, orderedCategories) => {
     // Optimistic: reorder items by new category order (Map preserves insertion order for numeric keys)
-    set(state => {
-      const grouped = new Map<string, BudgetItem[]>()
-      for (const item of state.budgetItems) {
-        const cat = item.category || 'Other'
-        if (!grouped.has(cat)) grouped.set(cat, [])
-        grouped.get(cat)!.push(item)
-      }
-      const reordered: BudgetItem[] = []
-      for (const cat of orderedCategories) {
-        const items = grouped.get(cat)
-        if (items) reordered.push(...items)
-      }
-      for (const [cat, items] of grouped) {
-        if (!orderedCategories.includes(cat)) reordered.push(...items)
-      }
-      return { budgetItems: reordered }
-    })
+    set(state => ({ budgetItems: orderBudgetByCategories(state.budgetItems, orderedCategories) }))
     try {
       await budgetApi.reorderCategories(tripId, orderedCategories)
     } catch (err: unknown) {
diff --git a/client/src/store/slices/remoteEventHandler.ts b/client/src/store/slices/remoteEventHandler.ts
index 38acd8e3c..f719bbc06 100644
--- a/client/src/store/slices/remoteEventHandler.ts
+++ b/client/src/store/slices/remoteEventHandler.ts
@@ -6,6 +6,7 @@ import { offlineDb } from '../../db/offlineDb'
 import { useAuthStore } from '../authStore'
 import { mergeAssignmentPlace } from './placesSlice'
 import { withoutDay } from './daysSlice'
+import { orderBudgetByCategories } from './budgetOrder'
 
 type SetState = StoreApi<TripStoreState>['setState']
 type GetState = StoreApi<TripStoreState>['getState']
@@ -439,22 +440,7 @@ export const STATE_APPLIERS: Partial<Record<TrekWsTripEventName, StateApplier>>
       return { budgetItems: [...reordered, ...remaining].map((item, idx) => ({ ...item, sort_order: idx })) }
     }
     if (payload.orderedCategories) {
-      const orderedCategories = payload.orderedCategories as string[]
-      const grouped = new Map<string, BudgetItem[]>()
-      for (const item of state.budgetItems) {
-        const cat = item.category || 'Other'
-        if (!grouped.has(cat)) grouped.set(cat, [])
-        grouped.get(cat)!.push(item)
-      }
-      const reordered: BudgetItem[] = []
-      for (const cat of orderedCategories) {
-        const items = grouped.get(cat)
-        if (items) reordered.push(...items)
-      }
-      for (const [cat, items] of grouped) {
-        if (!orderedCategories.includes(cat)) reordered.push(...items)
-      }
-      return { budgetItems: reordered }
+      return { budgetItems: orderBudgetByCategories(state.budgetItems, payload.orderedCategories as string[]) }
     }
     return {}
   },