diff --git a/CHANGES.md b/CHANGES.md
index dd18563..b422f4b 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -6,6 +6,7 @@
 - Update the docs.
 - Add the GLD Endpoints and models.
 - Add GLD option to bulk endpoint.
+- Enhancement: Allow for unknown construction date (IMBRO/A).
 
 
 ## 0.66 (2024-12-05)
diff --git a/api/bro_upload/templates/move_GMW_Construction.html b/api/bro_upload/templates/move_GMW_Construction.html
index 5dc91d6..b956551 100644
--- a/api/bro_upload/templates/move_GMW_Construction.html
+++ b/api/bro_upload/templates/move_GMW_Construction.html
@@ -30,7 +30,11 @@
             <ns:maintenanceResponsibleParty>{{ sourcedocs_data.maintenanceResponsibleParty }}</ns:maintenanceResponsibleParty>
             <ns:wellHeadProtector codeSpace="urn:bro:gmw:WellHeadProtector">{{ sourcedocs_data.wellHeadProtector }}</ns:wellHeadProtector>
             <ns:wellConstructionDate>
+{%              if not sourcedocs_data.wellConstructionDate %}
+                <ns1:date>onbekend</ns1:date>
+{%              elif sourcedocs_data.wellConstructionDate  %}
                 <ns1:date>{{ sourcedocs_data.wellConstructionDate }}</ns1:date>
+{%              endif %}
             </ns:wellConstructionDate>
             <ns:deliveredLocation>
                 <ns2:location ns3:id="id-f072811a-323d-40f4-8ebc-7fb0df43c660" srsName="urn:ogc:def:crs:EPSG::28992">
diff --git a/api/bro_upload/templates/registration_GMW_Construction.html b/api/bro_upload/templates/registration_GMW_Construction.html
index b614d65..ab30866 100644
--- a/api/bro_upload/templates/registration_GMW_Construction.html
+++ b/api/bro_upload/templates/registration_GMW_Construction.html
@@ -28,7 +28,11 @@
             <ns:maintenanceResponsibleParty>{{ sourcedocs_data.maintenanceResponsibleParty }}</ns:maintenanceResponsibleParty>
             <ns:wellHeadProtector codeSpace="urn:bro:gmw:WellHeadProtector">{{ sourcedocs_data.wellHeadProtector }}</ns:wellHeadProtector>
             <ns:wellConstructionDate>
+{%              if not sourcedocs_data.wellConstructionDate %}
+                <ns1:date>onbekend</ns1:date>
+{%              elif sourcedocs_data.wellConstructionDate  %}
                 <ns1:date>{{ sourcedocs_data.wellConstructionDate }}</ns1:date>
+{%              endif %}
             </ns:wellConstructionDate>
             <ns:deliveredLocation>
                 <ns2:location ns3:id="id-f072811a-323d-40f4-8ebc-7fb0df43c660" srsName="urn:ogc:def:crs:EPSG::28992">
diff --git a/api/bro_upload/templates/replace_GMW_Construction.html b/api/bro_upload/templates/replace_GMW_Construction.html
index 51a3723..ea25406 100644
--- a/api/bro_upload/templates/replace_GMW_Construction.html
+++ b/api/bro_upload/templates/replace_GMW_Construction.html
@@ -30,7 +30,11 @@
             <ns:maintenanceResponsibleParty>{{ sourcedocs_data.maintenanceResponsibleParty }}</ns:maintenanceResponsibleParty>
             <ns:wellHeadProtector codeSpace="urn:bro:gmw:WellHeadProtector">{{ sourcedocs_data.wellHeadProtector }}</ns:wellHeadProtector>
             <ns:wellConstructionDate>
+{%              if not sourcedocs_data.wellConstructionDate %}
+                <ns1:date>onbekend</ns1:date>
+{%              elif sourcedocs_data.wellConstructionDate  %}
                 <ns1:date>{{ sourcedocs_data.wellConstructionDate }}</ns1:date>
+{%              endif %}
             </ns:wellConstructionDate>
             <ns:deliveredLocation>
                 <ns2:location ns3:id="id-f072811a-323d-40f4-8ebc-7fb0df43c660" srsName="urn:ogc:def:crs:EPSG::28992">