diff --git a/CHANGELOG.md b/CHANGELOG.md
index ba8e24280..035a5e880 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@ and the versioning aims to respect [Semantic Versioning](http://semver.org/spec/
 ### Added
 - economic instrument, voluntary agreement, voluntary agreement instrument, regulatory instrument, information instrument, education instrument (#1786)
 - priority region role, priority region, conditionally reserved region role, conditionally reserved region, suitable region role, suitable region, priority region with effect of suitable region, spatial planning policy (#1791)
+- - missing value reason, notation key (#1795)
 
 ### Changed
 - energy transfer function, energy transformation function and subclasses (#1785)
diff --git a/src/ontology/edits/oeo-model.omn b/src/ontology/edits/oeo-model.omn
index c40bc9305..2539f1bfe 100644
--- a/src/ontology/edits/oeo-model.omn
+++ b/src/ontology/edits/oeo-model.omn
@@ -1657,6 +1657,33 @@ pull request: https://github.com/OpenEnergyPlatform/ontology/pull/1255",
         <http://purl.obolibrary.org/obo/IAO_0000030>
     
     
+Class: OEO_00010468
+
+    Annotations: 
+        <http://purl.obolibrary.org/obo/IAO_0000115> "A missing value reason is a data item that is used to indicate that data is not available and to provide a specific reason explaining why a meaningful value is not available."@en,
+        <http://purl.obolibrary.org/obo/IAO_0000118> "absent data"@en,
+        <http://purl.obolibrary.org/obo/IAO_0000118> "missing data"@en,
+        <http://purl.obolibrary.org/obo/IAO_0000119> "Definition partly adapted from http://purl.obolibrary.org/obo/NCIT_C48655",
+        <http://purl.obolibrary.org/obo/IAO_0000233> "issue: https://github.com/OpenEnergyPlatform/ontology/issues/1765
+pull request: https://github.com/OpenEnergyPlatform/ontology/pull/1795",
+        rdfs:label "missing value reason"@en
+    
+    SubClassOf: 
+        <http://purl.obolibrary.org/obo/IAO_0000027>
+    
+    
+Class: OEO_00010469
+
+    Annotations: 
+        <http://purl.obolibrary.org/obo/IAO_0000115> "A notation key is a missing value reason defined by the UNFCCC to indicate why data is missing."@en,
+        <http://purl.obolibrary.org/obo/IAO_0000233> "issue: https://github.com/OpenEnergyPlatform/ontology/issues/1765
+pull request: https://github.com/OpenEnergyPlatform/ontology/pull/1795",
+        rdfs:label "notation key"@en
+    
+    SubClassOf: 
+        OEO_00010468
+    
+    
 Class: OEO_00020011
 
     SubClassOf: