diff --git a/app/actions/submissions.ts b/app/actions/submissions.ts
index 30587e8..9eb9fce 100644
--- a/app/actions/submissions.ts
+++ b/app/actions/submissions.ts
@@ -1,8 +1,8 @@
 "use server";
 
 import { db } from "@/db";
-import { submissions, answers } from "@/db/schema";
-import { and, count, eq, lt, lte, or } from "drizzle-orm";
+import { submissions } from "@/db/schema";
+import { and, eq } from "drizzle-orm";
 import { revalidatePath } from "next/cache";
 import { getServerSession } from "next-auth";
 import { authOptions } from "@/lib/auth/auth-options";
@@ -11,8 +11,8 @@ import { sse } from "@/lib/realtime/sse";
 import type { FormAnswerPayload } from "@/lib/form/form-answer-values";
 import {
   normalizeSubmissionAnswers,
-  type StoredAnswerSnapshot,
 } from "@/lib/form/submission-intake";
+import { writeSubmission } from "@/lib/form/submission-write";
 import { submissionWebhookMessage } from "@/lib/form/submission-webhook";
 import { isFormAcceptingSubmissions } from "@/lib/form/form-availability";
 
@@ -64,113 +64,13 @@ export async function submitForm(
     }
   }
 
-  const result = await db.transaction(async (tx) => {
-    const existingSubmission = form.allowMultipleSubmissions
-      ? targetSubmissionId
-        ? await tx.query.submissions.findFirst({
-            where: (submission, { eq, and }) =>
-              and(
-                eq(submission.id, targetSubmissionId),
-                eq(submission.formId, formId),
-                eq(submission.userDiscordId, discordId)
-              ),
-          })
-        : null
-      : await tx.query.submissions.findFirst({
-          where: (submission, { eq, and }) =>
-            and(eq(submission.formId, formId), eq(submission.userDiscordId, discordId)),
-        });
-
-    if (form.allowMultipleSubmissions && targetSubmissionId && !existingSubmission) {
-      throw new Error("ไม่พบคำตอบที่ต้องการแก้ไข");
-    }
-
-    let submissionId = "";
-    let submittedAt = new Date();
-    const isUpdate = Boolean(existingSubmission);
-    let oldAnswersDict: Record<string, StoredAnswerSnapshot> = {};
-
-    if (existingSubmission) {
-      submissionId = existingSubmission.id;
-      submittedAt = existingSubmission.submittedAt;
-
-      const oldAnswersList = await tx.query.answers.findMany({
-        where: (answer, { eq }) => eq(answer.submissionId, submissionId),
-      });
-
-      oldAnswersDict = oldAnswersList.reduce<Record<string, StoredAnswerSnapshot>>((acc, curr) => {
-        acc[curr.questionId] = {
-          value: curr.value,
-          imageCdnId: curr.imageCdnId ?? null,
-        };
-        return acc;
-      }, {});
-
-      const history = Array.isArray(existingSubmission.editHistory)
-        ? [...existingSubmission.editHistory]
-        : [];
-      history.push({
-        editedAt: new Date().toISOString(),
-        oldAnswers: oldAnswersDict,
-      });
-
-      await tx
-        .update(submissions)
-        .set({ editHistory: history })
-        .where(eq(submissions.id, submissionId));
-
-      await tx.delete(answers).where(eq(answers.submissionId, submissionId));
-    } else {
-      const [inserted] = await tx
-        .insert(submissions)
-        .values({
-          formId,
-          userDiscordId: discordId,
-          userName,
-        })
-        .returning();
-      submissionId = inserted.id;
-      submittedAt = inserted.submittedAt;
-    }
-
-    if (normalizedAnswers.length > 0) {
-      await tx.insert(answers).values(
-        normalizedAnswers.map((answer) => ({
-          submissionId,
-          questionId: answer.questionId,
-          value: answer.value,
-          imageCdnId: answer.imageCdnId,
-        }))
-      );
-    }
-
-    const [submissionStats] = await tx
-      .select({ totalAnswers: count() })
-      .from(submissions)
-      .where(eq(submissions.formId, formId));
-    const [queueStats] = await tx
-      .select({ queueNumber: count() })
-      .from(submissions)
-      .where(
-        and(
-          eq(submissions.formId, formId),
-          or(
-            lt(submissions.submittedAt, submittedAt),
-            and(
-              eq(submissions.submittedAt, submittedAt),
-              lte(submissions.id, submissionId)
-            )
-          )
-        )
-      );
-
-    return {
-      submissionId,
-      isUpdate,
-      oldAnswersDict,
-      totalAnswers: submissionStats.totalAnswers,
-      queueNumber: queueStats.queueNumber,
-    };
+  const result = await writeSubmission({
+    formId,
+    discordId,
+    userName,
+    allowMultipleSubmissions: form.allowMultipleSubmissions,
+    normalizedAnswers,
+    targetSubmissionId,
   });
 
   // Send Discord Webhook
diff --git a/app/form/client.tsx b/app/form/client.tsx
index 4230edb..22451ca 100644
--- a/app/form/client.tsx
+++ b/app/form/client.tsx
@@ -59,6 +59,7 @@ import {
 import { isImageOnlyResponse } from "@/lib/form/question-response-type";
 import {
   buildFormSchema,
+  formatQueuePosition,
   parseStoredDraft,
   prepareInitialState,
   type FormFillerClientProps,
@@ -451,7 +452,9 @@ export function FormFillerClient({
             <span>{questions.length} คำถาม</span>
             <span>{totalAnswers} คำตอบทั้งหมด</span>
             {queueNumber !== null && (
-              <Badge variant="outline">ลำดับของคุณ #{queueNumber + 1}</Badge>
+              <Badge variant="outline">
+                ลำดับของคุณ {formatQueuePosition(queueNumber)}
+              </Badge>
             )}
           </CardDescription>
         </CardHeader>
@@ -996,7 +999,7 @@ export function FormFillerClient({
               ส่งคำตอบแล้ว
             </AlertDialogTitle>
             <AlertDialogDescription>
-              บันทึกคำตอบของคุณเรียบร้อย คำตอบของคุณอยู่ลำดับที่ #{(queueNumber ?? 0) + 1} จากทั้งหมด{" "}
+              บันทึกคำตอบของคุณเรียบร้อย คำตอบของคุณอยู่ลำดับที่ {formatQueuePosition(queueNumber ?? 1)} จากทั้งหมด{" "}
               {totalAnswers} คำตอบ คุณสามารถแก้ไขได้คำตอบตอนไหนก็ได้ที่แบบฟอร์มยังเปิดอยู่
             </AlertDialogDescription>
           </AlertDialogHeader>
diff --git a/lib/form/form-client.ts b/lib/form/form-client.ts
index 78ac7ea..8915536 100644
--- a/lib/form/form-client.ts
+++ b/lib/form/form-client.ts
@@ -45,6 +45,10 @@ export type FormFillerClientProps = {
 
 export type FormValues = Record<string, string | string[] | undefined>;
 
+export function formatQueuePosition(queueNumber: number) {
+  return `#${queueNumber}`;
+}
+
 export type StoredDraft = {
   version: 1;
   answers: FormValues;
diff --git a/lib/form/submission-write.test.ts b/lib/form/submission-write.test.ts
new file mode 100644
index 0000000..5bdf846
--- /dev/null
+++ b/lib/form/submission-write.test.ts
@@ -0,0 +1,9 @@
+import { describe, expect, test } from "bun:test";
+import { formatQueuePosition } from "@/lib/form/form-client";
+
+describe("submission queue position", () => {
+  test("keeps the database one-based position unchanged", () => {
+    expect(formatQueuePosition(1)).toBe("#1");
+    expect(formatQueuePosition(12)).toBe("#12");
+  });
+});
diff --git a/lib/form/submission-write.ts b/lib/form/submission-write.ts
new file mode 100644
index 0000000..6e34d64
--- /dev/null
+++ b/lib/form/submission-write.ts
@@ -0,0 +1,141 @@
+import "server-only";
+
+import { db } from "@/db";
+import { answers, submissions } from "@/db/schema";
+import { and, count, eq, lt, lte, or } from "drizzle-orm";
+import type {
+  NormalizedSubmissionAnswer,
+  StoredAnswerSnapshot,
+} from "@/lib/form/submission-intake";
+
+export type SubmissionWriteResult = {
+  submissionId: string;
+  isUpdate: boolean;
+  oldAnswersDict: Record<string, StoredAnswerSnapshot>;
+  totalAnswers: number;
+  queueNumber: number;
+};
+
+export async function writeSubmission({
+  formId,
+  discordId,
+  userName,
+  allowMultipleSubmissions,
+  normalizedAnswers,
+  targetSubmissionId,
+}: {
+  formId: string;
+  discordId: string;
+  userName: string | null;
+  allowMultipleSubmissions: boolean;
+  normalizedAnswers: NormalizedSubmissionAnswer[];
+  targetSubmissionId?: string | null;
+}): Promise<SubmissionWriteResult> {
+  return db.transaction(async (tx) => {
+    const existingSubmission = allowMultipleSubmissions
+      ? targetSubmissionId
+        ? await tx.query.submissions.findFirst({
+            where: (submission, { eq, and }) =>
+              and(
+                eq(submission.id, targetSubmissionId),
+                eq(submission.formId, formId),
+                eq(submission.userDiscordId, discordId),
+              ),
+          })
+        : null
+      : await tx.query.submissions.findFirst({
+          where: (submission, { eq, and }) =>
+            and(eq(submission.formId, formId), eq(submission.userDiscordId, discordId)),
+        });
+
+    if (allowMultipleSubmissions && targetSubmissionId && !existingSubmission) {
+      throw new Error("ไม่พบคำตอบที่ต้องการแก้ไข");
+    }
+
+    let submissionId = "";
+    let submittedAt = new Date();
+    const isUpdate = Boolean(existingSubmission);
+    let oldAnswersDict: Record<string, StoredAnswerSnapshot> = {};
+
+    if (existingSubmission) {
+      submissionId = existingSubmission.id;
+      submittedAt = existingSubmission.submittedAt;
+
+      const oldAnswersList = await tx.query.answers.findMany({
+        where: (answer, { eq }) => eq(answer.submissionId, submissionId),
+      });
+
+      oldAnswersDict = oldAnswersList.reduce<Record<string, StoredAnswerSnapshot>>(
+        (acc, curr) => {
+          acc[curr.questionId] = {
+            value: curr.value,
+            imageCdnId: curr.imageCdnId ?? null,
+          };
+          return acc;
+        },
+        {},
+      );
+
+      const history = Array.isArray(existingSubmission.editHistory)
+        ? [...existingSubmission.editHistory]
+        : [];
+      history.push({
+        editedAt: new Date().toISOString(),
+        oldAnswers: oldAnswersDict,
+      });
+
+      await tx
+        .update(submissions)
+        .set({ editHistory: history })
+        .where(eq(submissions.id, submissionId));
+
+      await tx.delete(answers).where(eq(answers.submissionId, submissionId));
+    } else {
+      const [inserted] = await tx
+        .insert(submissions)
+        .values({ formId, userDiscordId: discordId, userName })
+        .returning();
+      submissionId = inserted.id;
+      submittedAt = inserted.submittedAt;
+    }
+
+    if (normalizedAnswers.length > 0) {
+      await tx.insert(answers).values(
+        normalizedAnswers.map((answer) => ({
+          submissionId,
+          questionId: answer.questionId,
+          value: answer.value,
+          imageCdnId: answer.imageCdnId,
+        })),
+      );
+    }
+
+    const [submissionStats] = await tx
+      .select({ totalAnswers: count() })
+      .from(submissions)
+      .where(eq(submissions.formId, formId));
+    const [queueStats] = await tx
+      .select({ queueNumber: count() })
+      .from(submissions)
+      .where(
+        and(
+          eq(submissions.formId, formId),
+          or(
+            lt(submissions.submittedAt, submittedAt),
+            and(
+              eq(submissions.submittedAt, submittedAt),
+              lte(submissions.id, submissionId),
+            ),
+          ),
+        ),
+      );
+
+    return {
+      submissionId,
+      isUpdate,
+      oldAnswersDict,
+      totalAnswers: submissionStats.totalAnswers,
+      queueNumber: queueStats.queueNumber,
+    };
+  });
+}