diff --git a/data/aux_fields.yaml b/data/aux_fields.yaml
index 3f90e05..24a0295 100644
--- a/data/aux_fields.yaml
+++ b/data/aux_fields.yaml
@@ -40,3 +40,29 @@
   description:
     - Free-form identifier for the physical storage location of the container.
     - Intended for inventory management workflows (e.g. "Shelf B3", "DB2/S4").
+
+- key: 5
+  name: purchase_time
+  type: timestamp
+  category: user_data
+  description:
+    - Timestamp when the material package was purchased by the customer.
+    - Not filled by the manufacturer, for customer private tracking only.
+
+- key: 6
+  name: purchase_price
+  type: number
+  category: user_data
+  description:
+    - Amount (of `purchase_currency`) the user paid for the material package.
+    - Not filled by the manufacturer, for customer private tracking only.
+
+- key: 7
+  name: purchase_currency
+  type: string
+  max_length: 3
+  category: user_data
+  description:
+    - Currency of `purchase_price`.
+    - Alphabetic code according to [ISO 4271](https://en.wikipedia.org/wiki/ISO_4217).
+    - Not filled by the manufacturer, for customer private tracking only.
diff --git a/docs_src/nfc_data_format.md b/docs_src/nfc_data_format.md
index 4c3a593..d6f01d6 100644
--- a/docs_src/nfc_data_format.md
+++ b/docs_src/nfc_data_format.md
@@ -199,6 +199,9 @@ The auxiliary section is intended for dynamic data - typically usage tracking.
 #### 6.1.1 Field list (SLA-specific)
 {{ fields_table("aux_fields", "sla") }}
 
+#### 6.1.1 Field list (user data)
+{{ fields_table("aux_fields", "user_data") }}
+
 ### 6.2 Vendor-specific fields
 Vendor-specific fields not specified in this document are permitted for keys specified by the following table. Vendors may contact the specification authority to be assigned a key range for them to use.
 
diff --git a/utils/schema/fields.schema.json b/utils/schema/fields.schema.json
index d7854a8..f4e1f72 100644
--- a/utils/schema/fields.schema.json
+++ b/utils/schema/fields.schema.json
@@ -212,6 +212,15 @@
                 },
                 "storage_location": {
                     "$ref": "field_types.schema.json#/definitions/string"
+                },
+                "purchase_time": {
+                    "$ref": "field_types.schema.json#/definitions/timestamp"
+                },
+                "purchase_price": {
+                    "$ref": "field_types.schema.json#/definitions/number"
+                },
+                "purchase_currency": {
+                    "$ref": "field_types.schema.json#/definitions/string"
                 }
             },
             "unevaluatedProperties": false