diff --git a/app/models/submitter.rb b/app/models/submitter.rb
index 0a7f70b8f..f3cdfd107 100644
--- a/app/models/submitter.rb
+++ b/app/models/submitter.rb
@@ -25,15 +25,17 @@
 #  account_id    :bigint           not null
 #  external_id   :string
 #  submission_id :bigint           not null
+#  template_id   :bigint
 #
 # Indexes
 #
 #  index_submitters_on_account_id_and_completed_at  (account_id,completed_at) WHERE (completed_at IS NOT NULL)
 #  index_submitters_on_account_id_and_id            (account_id,id)
-#  index_submitters_on_email                        (email)
+#  index_submitters_on_email_and_template_id        (email,template_id) WHERE (email IS NOT NULL)
 #  index_submitters_on_external_id                  (external_id)
 #  index_submitters_on_slug                         (slug) UNIQUE
 #  index_submitters_on_submission_id                (submission_id)
+#  index_submitters_on_template_id_and_id           (template_id,id)
 #
 # Foreign Keys
 #
@@ -68,6 +70,8 @@ class Submitter < ApplicationRecord
 
   scope :completed, -> { where.not(completed_at: nil) }
 
+  before_validation :set_template_id, on: :create
+
   after_destroy :anonymize_email_events, if: -> { Docuseal.multitenant? }
 
   def status
@@ -124,6 +128,10 @@ class Submitter < ApplicationRecord
 
   private
 
+  def set_template_id
+    self.template_id = submission&.template_id
+  end
+
   def anonymize_email_events
     email_events.each do |event|
       event.update!(email: Digest::MD5.base64digest(event.email))
diff --git a/db/migrate/20261025120000_add_template_id_to_submitters.rb b/db/migrate/20261025120000_add_template_id_to_submitters.rb
new file mode 100644
index 000000000..68ca00ad2
--- /dev/null
+++ b/db/migrate/20261025120000_add_template_id_to_submitters.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class AddTemplateIdToSubmitters < ActiveRecord::Migration[8.1]
+  def change
+    add_column :submitters, :template_id, :bigint, if_not_exists: true
+  end
+end
diff --git a/db/migrate/20261025120001_populate_submitter_template_id.rb b/db/migrate/20261025120001_populate_submitter_template_id.rb
new file mode 100644
index 000000000..c7f1f0ab7
--- /dev/null
+++ b/db/migrate/20261025120001_populate_submitter_template_id.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+class PopulateSubmitterTemplateId < ActiveRecord::Migration[8.1]
+  disable_ddl_transaction!
+
+  class MigrationSubmitter < ApplicationRecord
+    self.table_name = 'submitters'
+  end
+
+  class MigrationSubmission < ApplicationRecord
+    self.table_name = 'submissions'
+  end
+
+  def up
+    return if ENV['MULTITENANT'] == 'true'
+
+    max_id = MigrationSubmitter.maximum(:id)
+
+    return unless max_id
+
+    submission_template_id =
+      Arel::Nodes::Grouping.new(
+        MigrationSubmission.arel_table.project(MigrationSubmission.arel_table[:template_id])
+                           .where(MigrationSubmission.arel_table[:id].eq(MigrationSubmitter.arel_table[:submission_id]))
+                           .ast
+      )
+
+    (1..max_id).step(10_000) do |start_id|
+      MigrationSubmitter.where(template_id: nil, id: start_id...(start_id + 10_000))
+                        .update_all(template_id: submission_template_id)
+    end
+  end
+
+  def down
+    nil
+  end
+end
diff --git a/db/migrate/20261025120002_add_submitters_template_id_indexes.rb b/db/migrate/20261025120002_add_submitters_template_id_indexes.rb
new file mode 100644
index 000000000..f733e1dc5
--- /dev/null
+++ b/db/migrate/20261025120002_add_submitters_template_id_indexes.rb
@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class AddSubmittersTemplateIdIndexes < ActiveRecord::Migration[8.1]
+  def up
+    add_index :submitters, %i[email template_id], where: 'email IS NOT NULL', if_not_exists: true
+    add_index :submitters, %i[template_id id], if_not_exists: true
+    remove_index :submitters, :email, if_exists: true
+  end
+
+  def down
+    add_index :submitters, :email, if_not_exists: true
+    remove_index :submitters, %i[template_id id], if_exists: true
+    remove_index :submitters, %i[email template_id], if_exists: true
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 58fd3dc2d..6cad2cf49 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.1].define(version: 2026_09_30_061927) do
+ActiveRecord::Schema[8.1].define(version: 2026_10_25_120002) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "btree_gin"
   enable_extension "pg_catalog.plpgsql"
@@ -424,6 +424,7 @@ ActiveRecord::Schema[8.1].define(version: 2026_09_30_061927) do
     t.datetime "sent_at"
     t.string "slug", null: false
     t.bigint "submission_id", null: false
+    t.bigint "template_id"
     t.string "timezone"
     t.string "ua"
     t.datetime "updated_at", null: false
@@ -431,10 +432,11 @@ ActiveRecord::Schema[8.1].define(version: 2026_09_30_061927) do
     t.text "values", null: false
     t.index ["account_id", "completed_at"], name: "index_submitters_on_account_id_and_completed_at", where: "(completed_at IS NOT NULL)"
     t.index ["account_id", "id"], name: "index_submitters_on_account_id_and_id"
-    t.index ["email"], name: "index_submitters_on_email"
+    t.index ["email", "template_id"], name: "index_submitters_on_email_and_template_id", where: "(email IS NOT NULL)"
     t.index ["external_id"], name: "index_submitters_on_external_id"
     t.index ["slug"], name: "index_submitters_on_slug", unique: true
     t.index ["submission_id"], name: "index_submitters_on_submission_id"
+    t.index ["template_id", "id"], name: "index_submitters_on_template_id_and_id"
   end
 
   create_table "template_accesses", force: :cascade do |t|