diff --git a/app/controllers/dois_controller.rb b/app/controllers/dois_controller.rb
index c28b41134..05549c63a 100644
--- a/app/controllers/dois_controller.rb
+++ b/app/controllers/dois_controller.rb
@@ -217,7 +217,11 @@ def show
   def validate
     logger = Logger.new(STDOUT)
     # logger.info safe_params.inspect
-    @doi = Doi.new(safe_params.merge(only_validate: true))
+
+    doi = Doi.where(doi: params.dig(:data,:attributes,:doi)).first
+    exists = doi.present?
+
+    @doi = Doi.new(safe_params.merge(only_validate: true, exists: exists))
 
     authorize! :validate, @doi
 
diff --git a/app/models/doi.rb b/app/models/doi.rb
index 00bde26bd..3d63a5e36 100644
--- a/app/models/doi.rb
+++ b/app/models/doi.rb
@@ -64,6 +64,7 @@ class Doi < ActiveRecord::Base
 
   attribute :regenerate, :boolean, default: false
   attribute :only_validate, :boolean, default: false
+  attribute :exists, :boolean, default: false
   attribute :should_validate, :boolean, default: false
   attribute :agency, :string, default: "DataCite"
 
@@ -77,7 +78,7 @@ class Doi < ActiveRecord::Base
   # validates_presence_of :url, if: :is_registered_or_findable?
 
   # from https://www.crossref.org/blog/dois-and-matching-regular-expressions/ but using uppercase
-  validates_format_of :doi, :with => /\A10\.\d{4,5}\/[-\._;()\/:a-zA-Z0-9\*~\$\=]+\z/, :on => :create
+  validates_format_of :doi, :with => /\A10\.\d{4,5}\/[-\._;()\/:a-zA-Z0-9\*~\$\=]+\z/, :on => :create, unless: :exists
   validates_format_of :url, :with => /\A(ftp|http|https):\/\/[\S]+/ , if: :url?, message: "URL is not valid"
   validates_uniqueness_of :doi, message: "This DOI has already been taken", unless: :only_validate
   validates :last_landing_page_status, numericality: { only_integer: true }, if: :last_landing_page_status?
diff --git a/spec/requests/dois_spec.rb b/spec/requests/dois_spec.rb
index a1f27eafd..db23555f2 100644
--- a/spec/requests/dois_spec.rb
+++ b/spec/requests/dois_spec.rb
@@ -1435,6 +1435,36 @@
       end
     end
 
+    context 'when doi has unpermitted characters' do
+      let(:xml) { Base64.strict_encode64(file_fixture('datacite.xml').read) }
+      let(:valid_attributes) do
+        {
+          "data" => {
+            "type" => "dois",
+            "attributes" => {
+              "doi" => "10.14454/107+03",
+              "url" => "http://www.bl.uk/pdf/patspec.pdf",
+              "xml" => xml,
+              "source" => "test",
+              "event" => "publish"
+            }
+          }
+        }
+      end
+
+      before { post '/dois', params: valid_attributes.to_json, headers: headers }
+
+      it 'returns validation error' do
+        expect(json.dig('errors')).to eq([{"source"=>"doi", "title"=>"Is invalid"}])
+      end
+
+
+      it 'returns status code 422' do
+        expect(response).to have_http_status(422)
+      end
+
+    end
+
     context 'creators no xml' do
       let(:creators) { [{ "name"=>"Ollomi, Benjamin" }, { "name"=>"Duran, Patrick" }] }
       let(:valid_attributes) do
@@ -1600,6 +1630,28 @@
         end
       end
 
+      context 'validatation fails with unpermitted characters in new DOI' do
+        let(:xml) { ::Base64.strict_encode64(File.read(file_fixture('datacite.xml'))) }
+        let(:params) do
+          {
+            "data" => {
+              "type" => "dois",
+              "attributes" => {
+                "doi" => "10.14454/107+03",
+                "xml" => xml,
+              }
+            }
+          }
+        end
+
+        before { post '/dois/validate', params: params.to_json, headers: headers }
+
+        it 'returns validation error' do
+          expect(json.dig('errors')).to eq([{"source"=>"doi", "title"=>"Is invalid"}])
+        end
+  
+      end
+
       context 'validates schema 3' do
         let(:xml) { ::Base64.strict_encode64(File.read(file_fixture('datacite_schema_3.xml'))) }
         let(:params) do