diff --git a/certificates/admin.py b/certificates/admin.py
index de9ba72..f1eff8a 100644
--- a/certificates/admin.py
+++ b/certificates/admin.py
@@ -12,9 +12,7 @@ class CertificateTemplateAdmin(admin.ModelAdmin):
 
 @admin.register(CertificateInstance)
 class CertificateInstanceAdmin(admin.ModelAdmin):
-    list_display = ('process_instance', 'rendered_title', 'issued_at', 'approved')
+    list_display = ('process_instance', 'rendered_title', 'hologram_code', 'issued_at', 'approved')
     list_filter = ('approved', 'issued_at')
-    search_fields = ('process_instance__code', 'rendered_title')
+    search_fields = ('process_instance__code', 'rendered_title', 'hologram_code')
     autocomplete_fields = ('process_instance', 'template')
-
-
diff --git a/certificates/migrations/0003_alter_certificateinstance_hologram_code.py b/certificates/migrations/0003_alter_certificateinstance_hologram_code.py
new file mode 100644
index 0000000..00fb9cd
--- /dev/null
+++ b/certificates/migrations/0003_alter_certificateinstance_hologram_code.py
@@ -0,0 +1,18 @@
+# Generated by Django 5.2.4 on 2025-10-09 08:26
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('certificates', '0002_certificateinstance_hologram_code'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='certificateinstance',
+            name='hologram_code',
+            field=models.CharField(blank=True, max_length=50, null=True, unique=True, verbose_name='کد یکتا هولوگرام'),
+        ),
+    ]
diff --git a/certificates/models.py b/certificates/models.py
index a7afe72..c374035 100644
--- a/certificates/models.py
+++ b/certificates/models.py
@@ -28,7 +28,7 @@ class CertificateInstance(BaseModel):
     issued_at = models.DateField(auto_now_add=True, verbose_name='تاریخ صدور')
     approved = models.BooleanField(default=False, verbose_name='تایید شده')
     approved_at = models.DateTimeField(null=True, blank=True, verbose_name='تاریخ تایید')
-    hologram_code = models.CharField(max_length=50, null=True, blank=True, verbose_name='کد یکتا هولوگرام')
+    hologram_code = models.CharField(max_length=50, null=True, blank=True, verbose_name='کد یکتا هولوگرام', unique=True)
 
     class Meta:
         verbose_name = 'گواهی'
diff --git a/certificates/views.py b/certificates/views.py
index 5149334..c16e7e9 100644
--- a/certificates/views.py
+++ b/certificates/views.py
@@ -6,6 +6,7 @@ from django.urls import reverse
 from django.utils import timezone
 from django.template import Template, Context
 from django.utils.safestring import mark_safe
+from django.db import IntegrityError
 
 from processes.models import ProcessInstance, StepInstance
 from invoices.models import Invoice
@@ -157,15 +158,56 @@ def certificate_print(request, instance_id):
     if request.method == 'POST':
         # Save/update hologram code then print
         code = (request.POST.get('hologram_code') or '').strip()
-        if cert:
-            if code:
+        
+        if not code:
+            messages.error(request, 'کد یکتای هولوگرام الزامی است')
+            # Find certificate step to redirect back
+            certificate_step = instance.process.steps.filter(order=9).first()
+            if certificate_step and instance.current_step:
+                return redirect('processes:step_detail', instance_id=instance.id, step_id=certificate_step.id)
+            return redirect('processes:instance_summary', instance_id=instance.id)
+        
+        try:
+            if cert:
+                # Check if hologram code is already used by another certificate
+                if CertificateInstance.objects.filter(hologram_code=code).exclude(id=cert.id).exists():
+                    messages.error(request, 'این کد هولوگرام قبلاً استفاده شده است. لطفاً کد دیگری وارد کنید')
+                    # Find certificate step to redirect back
+                    certificate_step = instance.process.steps.filter(order=9).first()
+                    if certificate_step and instance.current_step:
+                        return redirect('processes:step_detail', instance_id=instance.id, step_id=certificate_step.id)
+                    return redirect('processes:instance_summary', instance_id=instance.id)
+                
                 cert.hologram_code = code
                 cert.save(update_fields=['hologram_code'])
-        else:
-            template = CertificateTemplate.objects.filter(is_active=True).order_by('-created').first()
-            if template:
-                title, body = _render_template(template, instance)
-                cert = CertificateInstance.objects.create(process_instance=instance, template=template, rendered_title=title, rendered_body=body, hologram_code=code or None)
+            else:
+                # Check if hologram code is already used
+                if CertificateInstance.objects.filter(hologram_code=code).exists():
+                    messages.error(request, 'این کد هولوگرام قبلاً استفاده شده است. لطفاً کد دیگری وارد کنید')
+                    # Find certificate step to redirect back
+                    certificate_step = instance.process.steps.filter(order=9).first()
+                    if certificate_step and instance.current_step:
+                        return redirect('processes:step_detail', instance_id=instance.id, step_id=certificate_step.id)
+                    return redirect('processes:instance_summary', instance_id=instance.id)
+                
+                template = CertificateTemplate.objects.filter(is_active=True).order_by('-created').first()
+                if template:
+                    title, body = _render_template(template, instance)
+                    cert = CertificateInstance.objects.create(
+                        process_instance=instance, 
+                        template=template, 
+                        rendered_title=title, 
+                        rendered_body=body, 
+                        hologram_code=code
+                    )
+        except IntegrityError:
+            messages.error(request, 'این کد هولوگرام قبلاً استفاده شده است. لطفاً کد دیگری وارد کنید')
+            # Find certificate step to redirect back
+            certificate_step = instance.process.steps.filter(order=9).first()
+            if certificate_step and instance.current_step:
+                return redirect('processes:step_detail', instance_id=instance.id, step_id=certificate_step.id)
+            return redirect('processes:instance_summary', instance_id=instance.id)
+        
         # proceed to rendering page after saving code
         return render(request, 'certificates/print.html', {
             'instance': instance,
diff --git a/db.sqlite3 b/db.sqlite3
index 088d726..18e25d4 100644
Binary files a/db.sqlite3 and b/db.sqlite3 differ