diff --git a/.gitignore b/.gitignore
index aa7de9a..fbd9f0d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 .DS_Store
 node_modules/
+assets/test-invoices/
 
 # Env files (never commit secrets)
 .env
diff --git a/apps/api/app/controllers/checkin_controller.ts b/apps/api/app/controllers/checkin_controller.ts
index 8311f90..829e656 100644
--- a/apps/api/app/controllers/checkin_controller.ts
+++ b/apps/api/app/controllers/checkin_controller.ts
@@ -16,12 +16,13 @@ const CHECKIN_TTL_HOURS = 24
  */
 function spaRedirectUrl(
   result: 'paid' | 'pending' | 'expired' | 'invalid' | 'already_answered',
-  invoiceNumero?: string
+  invoice?: Pick<Invoice, 'id' | 'numero'>
 ): string {
   const base = env.get('WEB_URL', 'http://localhost:5173')
   const params = new URLSearchParams({ checkin: result })
-  if (invoiceNumero) params.set('invoice', invoiceNumero)
-  return `${base}/?${params.toString()}`
+  if (invoice) params.set('invoice', invoice.numero)
+  const path = invoice ? `/factures/${invoice.id}` : '/'
+  return `${base}${path}?${params.toString()}`
 }
 
 type ResolvedTask = { task: CheckinTask; invoice: Invoice } | { redirect: string }
@@ -39,7 +40,7 @@ async function resolveCheckin(token: string): Promise<ResolvedTask> {
 
   if (task.status === 'answered') {
     const inv = await Invoice.find(task.invoiceId)
-    return { redirect: spaRedirectUrl('already_answered', inv?.numero) }
+    return { redirect: spaRedirectUrl('already_answered', inv ?? undefined) }
   }
 
   // Expiration : 24h après l'envoi (sentAt). Tant qu'elle n'a pas été
@@ -107,7 +108,7 @@ export default class CheckinController {
       }
     })
 
-    return response.redirect(spaRedirectUrl('paid', invoice.numero))
+    return response.redirect(spaRedirectUrl('paid', invoice))
   }
 
   /**
@@ -123,15 +124,19 @@ export default class CheckinController {
     }
     const { task, invoice } = result
 
-    task.status = 'answered'
-    task.answer = 'still_pending'
-    task.answeredAt = DateTime.now()
-    await task.save()
+    await db.transaction(async (trx) => {
+      if (invoice.planId) {
+        invoice.useTransaction(trx)
+        await scheduleRelancesForInvoice(invoice, trx)
+      }
 
-    if (invoice.planId) {
-      await scheduleRelancesForInvoice(invoice)
-    }
+      task.useTransaction(trx)
+      task.status = 'answered'
+      task.answer = 'still_pending'
+      task.answeredAt = DateTime.now()
+      await task.save()
+    })
 
-    return response.redirect(spaRedirectUrl('pending', invoice.numero))
+    return response.redirect(spaRedirectUrl('pending', invoice))
   }
 }
diff --git a/apps/api/app/services/relance_scheduler.ts b/apps/api/app/services/relance_scheduler.ts
index 621948a..db375ab 100644
--- a/apps/api/app/services/relance_scheduler.ts
+++ b/apps/api/app/services/relance_scheduler.ts
@@ -46,6 +46,13 @@ export async function scheduleRelancesForInvoice(
     .first()
   if (!plan) return []
 
+  const alreadyActive = await RelanceTask.query(trx ? { client: trx } : undefined)
+    .where('invoice_id', invoice.id)
+    .whereIn('status', ['scheduled', 'sent'])
+  if (alreadyActive.length > 0) {
+    return alreadyActive
+  }
+
   // Cancel les tasks scheduled existantes (re-scheduling après changement
   // de plan ou de dueDate).
   const existing = await RelanceTask.query(trx ? { client: trx } : undefined)
diff --git a/apps/web/src/routes/_app/factures_.$id.tsx b/apps/web/src/routes/_app/factures_.$id.tsx
index aee1cec..19c5c38 100644
--- a/apps/web/src/routes/_app/factures_.$id.tsx
+++ b/apps/web/src/routes/_app/factures_.$id.tsx
@@ -1,17 +1,14 @@
+import { useEffect } from "react";
 import { createFileRoute, Link, useNavigate } from "@tanstack/react-router";
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { ArrowLeft, Check, Send } from "lucide-react";
 import { toast } from "sonner";
+import { z } from "zod";
 
 import type { Client, Invoice, Plan } from "@rubis/shared";
 import { api } from "@/lib/api";
 import { queryKeys } from "@/lib/queryKeys";
-import {
-  formatEuros,
-  formatDate,
-  formatDueDelta,
-  isOverdue,
-} from "@/lib/format";
+import { formatEuros, formatDate, formatDueDelta, isOverdue } from "@/lib/format";
 
 import { Button } from "@/components/ui/Button";
 import { Card } from "@/components/ui/Card";
@@ -20,6 +17,11 @@ import { StatusBadge } from "@/components/ui/StatusBadge";
 import { Timeline, type TimelineEvent } from "@/components/ui/Timeline";
 import { Textarea } from "@/components/ui/Textarea";
 
+const checkinSearchSchema = z.object({
+  checkin: z.enum(["paid", "pending", "expired", "invalid", "already_answered"]).optional(),
+  invoice: z.string().optional(),
+});
+
 type InvoiceDetail = Invoice & {
   client: Client;
   plan: Plan | null;
@@ -29,6 +31,7 @@ type InvoiceDetail = Invoice & {
 };
 
 export const Route = createFileRoute("/_app/factures_/$id")({
+  validateSearch: checkinSearchSchema,
   component: InvoiceDetailPage,
   loader: ({ context, params }) => {
     void context.queryClient.prefetchQuery({
@@ -40,10 +43,15 @@ export const Route = createFileRoute("/_app/factures_/$id")({
 
 function InvoiceDetailPage() {
   const { id } = Route.useParams();
+  const search = Route.useSearch();
   const queryClient = useQueryClient();
   const navigate = useNavigate();
 
-  const { data: invoice, isPending, isError } = useQuery({
+  const {
+    data: invoice,
+    isPending,
+    isError,
+  } = useQuery({
     queryKey: queryKeys.invoices.detail(id),
     queryFn: () => api.get<InvoiceDetail>(`/api/v1/invoices/${id}`),
   });
@@ -61,12 +69,37 @@ function InvoiceDetailPage() {
     },
   });
 
+  useEffect(() => {
+    const checkin = search.checkin;
+    if (!checkin) return;
+
+    const labels: Record<typeof checkin, string> = {
+      paid: "Facture marquée encaissée.",
+      pending: "Relance activée pour cette facture.",
+      expired: "Ce lien de check-in a expiré.",
+      invalid: "Ce lien de check-in est invalide.",
+      already_answered: "Ce check-in avait déjà été traité.",
+    };
+
+    const isErrorToast = checkin === "expired" || checkin === "invalid";
+    if (isErrorToast) toast.error(labels[checkin]);
+    else toast.success(labels[checkin]);
+
+    void queryClient.invalidateQueries({ queryKey: queryKeys.invoices.detail(id) });
+    void queryClient.invalidateQueries({ queryKey: queryKeys.invoices.all() });
+    void queryClient.invalidateQueries({ queryKey: queryKeys.dashboard.kpis() });
+    void navigate({
+      to: "/factures/$id",
+      params: { id },
+      search: {},
+      replace: true,
+    });
+  }, [id, navigate, queryClient, search.checkin]);
+
   if (isError) {
     return (
       <div className="text-center py-12">
-        <p className="font-display text-[20px] font-semibold text-ink">
-          Facture introuvable.
-        </p>
+        <p className="font-display text-[20px] font-semibold text-ink">Facture introuvable.</p>
         <Link
           to="/factures"
           className="mt-3 inline-block text-[13px] text-rubis underline-offset-4 hover:underline"
@@ -117,11 +150,7 @@ function InvoiceDetailPage() {
                 ({formatDueDelta(invoice.dueDate)})
               </span>
             </span>
-            <StatusBadge
-              status={invoice.status}
-              label={invoice.statusLabel}
-              className="ml-1"
-            />
+            <StatusBadge status={invoice.status} label={invoice.statusLabel} className="ml-1" />
           </p>
         </div>
 
@@ -147,9 +176,7 @@ function InvoiceDetailPage() {
         <Card padding="md">
           <Eyebrow tone="ink">
             Timeline
-            {invoice.plan && (
-              <span className="text-ink-3"> · plan {invoice.plan.name}</span>
-            )}
+            {invoice.plan && <span className="text-ink-3"> · plan {invoice.plan.name}</span>}
           </Eyebrow>
           <Timeline events={invoice.timeline} className="mt-5" />
         </Card>
@@ -162,14 +189,10 @@ function InvoiceDetailPage() {
               {invoice.client.name}
             </p>
             {invoice.client.email && (
-              <p className="mt-1 text-[13.5px] text-ink-2 truncate">
-                {invoice.client.email}
-              </p>
+              <p className="mt-1 text-[13.5px] text-ink-2 truncate">{invoice.client.email}</p>
             )}
             {invoice.client.phone && (
-              <p className="mt-0.5 text-[13.5px] text-ink-2">
-                {invoice.client.phone}
-              </p>
+              <p className="mt-0.5 text-[13.5px] text-ink-2">{invoice.client.phone}</p>
             )}
             {invoice.client.address && (
               <p className="mt-2 text-[12.5px] leading-relaxed text-ink-3">