diff --git a/.ruby-version b/.ruby-version
index acf9bf0..1454f6e 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.2.2
\ No newline at end of file
+4.0.1
diff --git a/lib/dvla/atlas/artefacts.rb b/lib/dvla/atlas/artefacts.rb
index 4721b04..81422d8 100644
--- a/lib/dvla/atlas/artefacts.rb
+++ b/lib/dvla/atlas/artefacts.rb
@@ -19,6 +19,19 @@ def define_fields(*vargs, **kwargs)
         end
       end
 
+      sig { params(_options: T.untyped).returns(T::Hash[String, T.untyped]) }
+      def as_json(_options = nil)
+        instance_variables.each_with_object({}) do |var, hash|
+          name = var.to_s.delete_prefix('@')
+          value = send(:"#{name}")
+
+          next if value.nil?
+          next if name.end_with?('_history') && value.empty?
+
+          hash[name] = value
+        end
+      end
+
     private
 
       sig { params(name: T.any(String, Symbol)).void }
diff --git a/lib/dvla/atlas/version.rb b/lib/dvla/atlas/version.rb
index 2de81ab..b1b314a 100644
--- a/lib/dvla/atlas/version.rb
+++ b/lib/dvla/atlas/version.rb
@@ -1,5 +1,5 @@
 module DVLA
   module Atlas
-    VERSION = '1.1.0'.freeze
+    VERSION = '1.1.1'.freeze
   end
 end
diff --git a/spec/dvla/atlas/artefacts_spec.rb b/spec/dvla/atlas/artefacts_spec.rb
index e2f9d6c..9aa5c03 100644
--- a/spec/dvla/atlas/artefacts_spec.rb
+++ b/spec/dvla/atlas/artefacts_spec.rb
@@ -121,4 +121,25 @@
     expect(artefacts.first_expected_method_history).to eq(%w[abc])
     expect(artefacts.second_expected_method_history).to eq([123])
   end
+
+  describe '#as_json' do
+    it 'excludes fields that are nil' do
+      artefacts.define_fields('unset_field', set_field: 'value')
+      expect(artefacts.as_json).to eq({ 'set_field' => 'value' })
+    end
+
+    it 'excludes history fields for fields that have never been changed' do
+      artefacts.define_fields(username: 'initial')
+      json = artefacts.as_json
+      expect(json).to eq({ 'username' => 'initial' })
+      expect(json).not_to have_key('username_history')
+    end
+
+    it 'includes history fields for fields that have been changed' do
+      artefacts.define_fields(username: 'initial')
+      artefacts.username = 'updated'
+      json = artefacts.as_json
+      expect(json).to eq({ 'username' => 'updated', 'username_history' => ['initial'] })
+    end
+  end
 end