diff --git a/app/models/completed_submitter.rb b/app/models/completed_submitter.rb
index 25c36e3a..a72e92be 100644
--- a/app/models/completed_submitter.rb
+++ b/app/models/completed_submitter.rb
@@ -6,6 +6,7 @@
 #
 #  id                  :bigint           not null, primary key
 #  completed_at        :datetime         not null
+#  is_first            :boolean
 #  sms_count           :integer          not null
 #  source              :string           not null
 #  verification_method :string
@@ -18,8 +19,10 @@
 #
 # Indexes
 #
-#  index_completed_submitters_on_account_id    (account_id)
-#  index_completed_submitters_on_submitter_id  (submitter_id) UNIQUE
+#  index_completed_submitters_on_account_id                   (account_id)
+#  index_completed_submitters_on_account_id_and_completed_at  (account_id,completed_at) WHERE (is_first = true)
+#  index_completed_submitters_on_submission_id                (submission_id) UNIQUE WHERE (is_first = true)
+#  index_completed_submitters_on_submitter_id                 (submitter_id) UNIQUE
 #
 class CompletedSubmitter < ApplicationRecord
   belongs_to :submitter
diff --git a/db/migrate/20251121092044_add_is_first_to_completed_submitters.rb b/db/migrate/20251121092044_add_is_first_to_completed_submitters.rb
new file mode 100644
index 00000000..393484e9
--- /dev/null
+++ b/db/migrate/20251121092044_add_is_first_to_completed_submitters.rb
@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class AddIsFirstToCompletedSubmitters < ActiveRecord::Migration[8.0]
+  def change
+    # rubocop:disable Rails/ThreeStateBooleanColumn
+    add_column :completed_submitters, :is_first, :boolean
+    # rubocop:enable Rails/ThreeStateBooleanColumn
+
+    add_index :completed_submitters, %i[account_id completed_at], where: 'is_first = TRUE'
+    add_index :completed_submitters, :submission_id, unique: true, where: 'is_first = TRUE'
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 786d7863..1814f5d8 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[8.0].define(version: 2025_11_21_090556) do
+ActiveRecord::Schema[8.0].define(version: 2025_11_21_092044) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "btree_gin"
   enable_extension "plpgsql"
@@ -118,7 +118,10 @@ ActiveRecord::Schema[8.0].define(version: 2025_11_21_090556) do
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.string "verification_method"
+    t.boolean "is_first"
+    t.index ["account_id", "completed_at"], name: "index_completed_submitters_on_account_id_and_completed_at", where: "(is_first = true)"
     t.index ["account_id"], name: "index_completed_submitters_on_account_id"
+    t.index ["submission_id"], name: "index_completed_submitters_on_submission_id", unique: true, where: "(is_first = true)"
     t.index ["submitter_id"], name: "index_completed_submitters_on_submitter_id", unique: true
   end