diff --git a/lib/secretariat/constants.rb b/lib/secretariat/constants.rb
index 1445064..1777244 100644
--- a/lib/secretariat/constants.rb
+++ b/lib/secretariat/constants.rb
@@ -96,4 +96,12 @@ module Secretariat
     :TON => "TNE",
     :WEEK => "WEE"
   }
+
+  SPECIFICATION_IDS = {
+    :XRECHNUNG_3_0 => "urn:cen.eu:en16931:2017#compliant#urn:xeinkauf.de:kosit:xrechnung_3.0"
+  }
+
+  BUSINESS_PROCESS_IDS = {
+    :PEPPOL_BILLING => "urn:fdc:peppol.eu:2017:poacc:billing:01:1.0"
+  }
 end
diff --git a/lib/secretariat/invoice.rb b/lib/secretariat/invoice.rb
index 140627b..08bc0a7 100644
--- a/lib/secretariat/invoice.rb
+++ b/lib/secretariat/invoice.rb
@@ -20,6 +20,8 @@ module Secretariat
   using ObjectExtensions
   
   Invoice = Struct.new("Invoice",
+    :specification_id,
+    :business_process_id,
     :id,
     :issue_date,
     :service_period_start,
@@ -199,9 +201,14 @@ def to_xml(version: 1, validate: true)
           context = by_version(version, 'SpecifiedExchangedDocumentContext', 'ExchangedDocumentContext')
 
           xml['rsm'].send(context) do
+            if business_process_id.present?
+              xml['ram'].BusinessProcessSpecifiedDocumentContextParameter do
+                xml['ram'].ID business_process_id
+              end
+            end
             xml['ram'].GuidelineSpecifiedDocumentContextParameter do
               version_id = by_version(version, 'urn:ferd:CrossIndustryDocument:invoice:1p0:comfort', 'urn:cen.eu:en16931:2017')
-              xml['ram'].ID version_id
+              xml['ram'].ID specification_id || version_id
             end
           end
 
diff --git a/test/invoice_test.rb b/test/invoice_test.rb
index 8af2c76..1b07543 100644
--- a/test/invoice_test.rb
+++ b/test/invoice_test.rb
@@ -884,5 +884,28 @@ def test_invoice_with_quantity_causing_sub_cent_amounts
       end
       assert_equal [], errors
     end
+
+    def test_default_specification_id
+      xml = make_de_invoice.to_xml(version: 2)
+
+      assert_match(/<ram:GuidelineSpecifiedDocumentContextParameter>\s*<ram:ID>urn:cen.eu:en16931:2017<\/ram:ID>/, xml)
+    end
+
+    def test_custom_specification_id
+      invoice = make_de_invoice
+      invoice.specification_id = SPECIFICATION_IDS[:XRECHNUNG_3_0]
+      xml = invoice.to_xml(version: 2)
+
+      assert_match(/<ram:ID>#{Regexp.escape(SPECIFICATION_IDS[:XRECHNUNG_3_0])}<\/ram:ID>/, xml)
+    end
+
+    def test_business_process_id
+      invoice = make_de_invoice
+      invoice.business_process_id = BUSINESS_PROCESS_IDS[:PEPPOL_BILLING]
+      xml = invoice.to_xml(version: 2)
+
+      assert_match(/<ram:BusinessProcessSpecifiedDocumentContextParameter>\s*<ram:ID>#{Regexp.escape(BUSINESS_PROCESS_IDS[:PEPPOL_BILLING])}<\/ram:ID>/, xml)
+      assert_equal [], Validator.new(xml, version: 2).validate_against_schema
+    end
   end
 end