diff --git a/src/__tests__/numbering.test.ts b/src/__tests__/numbering.test.ts
index aa39246..dfd8444 100644
--- a/src/__tests__/numbering.test.ts
+++ b/src/__tests__/numbering.test.ts
@@ -2,6 +2,8 @@ import { describe, it, expect, beforeEach, afterEach } from "vitest";
 import {
   generateSharedNumber,
   generateOfferNumber,
+  previewSharedNumber,
+  isSharedNumberTaken,
 } from "../services/numbering.service";
 import prisma from "../config/database";
 
@@ -48,3 +50,43 @@ describe("generateOfferNumber", () => {
     expect(num1).not.toBe(num2);
   });
 });
+
+describe("previewSharedNumber", () => {
+  let createdProjectId: number | null = null;
+
+  beforeEach(async () => {
+    await prisma.number_sequences.deleteMany({ where: { type: "shared" } });
+  });
+
+  afterEach(async () => {
+    if (createdProjectId !== null) {
+      await prisma.projects
+        .delete({ where: { id: createdProjectId } })
+        .catch(() => {});
+      createdProjectId = null;
+    }
+    await prisma.number_sequences.deleteMany({ where: { type: "shared" } });
+  });
+
+  it("returns a number not already used by an order or project", async () => {
+    const preview = await previewSharedNumber();
+    expect(typeof preview).toBe("string");
+    expect(await isSharedNumberTaken(preview)).toBe(false);
+  });
+
+  it("skips a number already taken when the sequence counter lags behind", async () => {
+    // Fresh counter → preview points at the first sequence number. With the
+    // skip-taken logic this is guaranteed free, so we can safely claim it.
+    const first = await previewSharedNumber();
+    const project = await prisma.projects.create({
+      data: { project_number: first, name: "test-preview-skip-taken" },
+    });
+    createdProjectId = project.id;
+
+    // The counter still lags behind (no row was consumed), but `first` is now
+    // taken — the preview must advance past it instead of re-offering it.
+    const second = await previewSharedNumber();
+    expect(second).not.toBe(first);
+    expect(await isSharedNumberTaken(second)).toBe(false);
+  });
+});
diff --git a/src/services/numbering.service.ts b/src/services/numbering.service.ts
index 333f5d2..5a07c23 100644
--- a/src/services/numbering.service.ts
+++ b/src/services/numbering.service.ts
@@ -258,7 +258,18 @@ export async function previewSharedNumber(): Promise<string> {
   const code = settings?.order_type_code || "71";
   const year = new Date().getFullYear();
 
-  const seq = await previewNextSequence("shared", year);
+  // Mirror generateSharedNumber's collision check (without consuming the
+  // sequence). The number_sequences counter can lag behind real data — e.g.
+  // when orders/projects were imported or seeded without bumping it — so the
+  // raw next sequence may already be taken. Advance past any number already
+  // used by an order or project, so the preview matches what generateSharedNumber
+  // would actually assign instead of showing a stale, already-used number.
+  let seq = await previewNextSequence("shared", year);
+  for (let attempt = 0; attempt < 1000; attempt++) {
+    const number = applyPattern(pattern, { year, prefix: "", code, seq });
+    if (!(await isSharedNumberTaken(number))) return number;
+    seq++;
+  }
   return applyPattern(pattern, { year, prefix: "", code, seq });
 }