diff --git a/lib/tasks/backfill_sponsor_id.rake b/lib/tasks/backfill_sponsor_id.rake
new file mode 100644
index 00000000000..f3463f13440
--- /dev/null
+++ b/lib/tasks/backfill_sponsor_id.rake
@@ -0,0 +1,48 @@
+# frozen_string_literal: true
+
+namespace :in_person_enrollments do
+  desc 'Backfill the sponsor_id column.'
+
+  ##
+  # Usage:
+  #
+  # bundle exec rake in_person_enrollments:backfill_sponsor_id
+  #
+  task backfill_sponsor_id: :environment do |_task, _args|
+    with_timeout do
+      ipp_sponsor_id = IdentityConfig.store.usps_ipp_sponsor_id
+      enrollments_without_sponsor_id = InPersonEnrollment.where(sponsor_id: nil)
+      enrollments_without_sponsor_id_count = enrollments_without_sponsor_id.count
+
+      warn("Found #{enrollments_without_sponsor_id_count} in_person_enrollments needing backfill")
+
+      tally = 0
+      enrollments_without_sponsor_id.in_batches(of: batch_size) do |batch|
+        tally += batch.update_all(sponsor_id: ipp_sponsor_id) # rubocop:disable Rails/SkipsModelValidations
+        warn("set sponsor_id for #{tally} in_person_enrollments")
+      end
+      warn("COMPLETE: Updated #{tally} in_person_enrollments")
+
+      enrollments_without_sponsor_id = InPersonEnrollment.where(sponsor_id: nil)
+      enrollments_without_sponsor_id_count = enrollments_without_sponsor_id.count
+      warn("#{enrollments_without_sponsor_id_count} enrollments without a sponsor id")
+    end
+  end
+
+  def batch_size
+    ENV['BATCH_SIZE'] ? ENV['BATCH_SIZE'].to_i : 1000
+  end
+
+  def with_timeout
+    timeout_in_seconds ||= if ENV['STATEMENT_TIMEOUT_IN_SECONDS']
+                             ENV['STATEMENT_TIMEOUT_IN_SECONDS'].to_i.seconds
+                          else
+                            60.seconds
+                          end
+    ActiveRecord::Base.transaction do
+      quoted_timeout = ActiveRecord::Base.connection.quote(timeout_in_seconds.in_milliseconds)
+      ActiveRecord::Base.connection.execute("SET statement_timeout = #{quoted_timeout}")
+      yield
+    end
+  end
+end
diff --git a/spec/factories/in_person_enrollments.rb b/spec/factories/in_person_enrollments.rb
index 6e691db084d..70238b182c2 100644
--- a/spec/factories/in_person_enrollments.rb
+++ b/spec/factories/in_person_enrollments.rb
@@ -46,5 +46,9 @@
     trait :enhanced_ipp do
       sponsor_id { IdentityConfig.store.usps_eipp_sponsor_id }
     end
+
+    trait :with_nil_sponsor_id do
+      sponsor_id { nil }
+    end
   end
 end
diff --git a/spec/lib/tasks/backfill_sponsor_id_rake_spec.rb b/spec/lib/tasks/backfill_sponsor_id_rake_spec.rb
new file mode 100644
index 00000000000..2992ff7bd27
--- /dev/null
+++ b/spec/lib/tasks/backfill_sponsor_id_rake_spec.rb
@@ -0,0 +1,73 @@
+require 'rails_helper'
+require 'rake'
+
+RSpec.describe 'in_person_enrollments:backfill_sponsor_id rake task' do
+  let!(:task) do
+    Rake.application.rake_require 'tasks/backfill_sponsor_id'
+    Rake::Task.define_task(:environment)
+    Rake::Task['in_person_enrollments:backfill_sponsor_id']
+  end
+
+  subject(:invoke_task) do
+    actual_stderr = $stderr
+    proxy_stderr = StringIO.new
+    begin
+      $stderr = proxy_stderr
+      task.reenable
+      task.invoke
+      proxy_stderr.string
+    ensure
+      $stderr = actual_stderr
+    end
+  end
+
+  let(:pending_enrollment) { create(:in_person_enrollment, :pending, :with_nil_sponsor_id) }
+  let(:expired_enrollment) { create(:in_person_enrollment, :expired, :with_nil_sponsor_id) }
+  let(:failed_enrollment) { create(:in_person_enrollment, :failed, :with_nil_sponsor_id) }
+  let(:enrollment_with_service_provider) do
+    create(:in_person_enrollment, :with_service_provider, :with_nil_sponsor_id)
+  end
+  let(:enrollment_with_sponsor_id) { create(:in_person_enrollment) }
+
+  before do
+    allow(IdentityConfig.store).to receive(:usps_ipp_sponsor_id).and_return('31459')
+    expect(pending_enrollment.sponsor_id).to be_nil
+    expect(expired_enrollment.sponsor_id).to be_nil
+    expect(failed_enrollment.sponsor_id).to be_nil
+    expect(enrollment_with_service_provider.sponsor_id).to be_nil
+    expect(enrollment_with_sponsor_id.sponsor_id).not_to be_nil
+  end
+
+  it 'does not change the value of an existing sponsor id' do
+    original_sponsor_id = enrollment_with_sponsor_id.sponsor_id
+    subject
+    expect(enrollment_with_sponsor_id.sponsor_id).to eq(original_sponsor_id)
+  end
+
+  it 'sets a sponsor id for every enrollment with a nil sponsor id' do
+    enrollments_with_nil_sponsor_id_count = InPersonEnrollment.where(sponsor_id: nil).count
+    expect(enrollments_with_nil_sponsor_id_count).to eq(4)
+    subject
+    enrollments_with_nil_sponsor_id_count = InPersonEnrollment.where(sponsor_id: nil).count
+    expect(enrollments_with_nil_sponsor_id_count).to eq(0)
+  end
+
+  it 'sets a sponsor id that is a string' do
+    subject
+    enrollments = InPersonEnrollment.all
+    enrollments.each do |enrollment|
+      expect(enrollment.sponsor_id).to be_a String
+    end
+  end
+
+  it 'outputs what it did' do
+    expect(invoke_task.to_s).to eql(
+      <<~END,
+        Found 4 in_person_enrollments needing backfill
+        set sponsor_id for 4 in_person_enrollments
+        COMPLETE: Updated 4 in_person_enrollments
+        0 enrollments without a sponsor id
+      END
+    )
+  end
+end