diff --git a/openapi/activation.openapi.yaml b/openapi/activation.openapi.yaml
index 6561e35..77db3d4 100644
--- a/openapi/activation.openapi.yaml
+++ b/openapi/activation.openapi.yaml
@@ -456,6 +456,14 @@ components:
     # --------------------------------------------------------------------------
     # Domain specific basic types.
     # --------------------------------------------------------------------------
+    Bic:
+      description: Bank Identification Code.
+      type: string
+      pattern: "^[A-Z0-9]{4}[A-Z]{2}[A-Z0-9]{2}([A-Z0-9]{3}){0,1}$"
+      minLength: 8
+      maxLength: 11
+      example: "UNCRITMM"
+        
     EffectiveActivationDate:
       description: |
         Effective activation date (B035).
@@ -467,7 +475,7 @@ components:
 
     FiscalCode:
       description: |
-        Fiscal (or tax) code.
+        Fiscal code.
         
         It is used as identifier of the Payer (P009) and of the Payee (E005).
       type: string
@@ -476,17 +484,29 @@ components:
       maxLength: 16
       example: "RSSMRA85T10A562S"
 
+    Lei:
+      description: |
+        Legal Entity Identifier is a code allocated to a party as described in
+        ISO 17442 "Financial Services - Legal Entity Identifier (LEI)".
+      type: string
+      pattern: "^[A-Z0-9]{18}[0-9]{2}$"
+      minLength: 20
+      maxLength: 20
+      example: "984500A9EB6B07AC2G71"
+
     PartyId:
       description: |
         Unique and unambiguous identification of a party.
         
         It is used as identifier of the Payer’s RTP Service Provider (N001) and
         for Payee’s RTP Service Provider (N002).
-      type: string
-      pattern: "^[ -~]{1,35}$"
-      minLength: 1
-      maxLength: 35
-      example: "12345678901"
+        
+        A Service Provider is identified by its BIC (Bank Identification Code)
+        if it is a PSP, otherwise it is identified by its LEI (Legal Entity
+        Identifier).
+      oneOf:
+        - $ref: '#/components/schemas/Bic'
+        - $ref: '#/components/schemas/Lei'
 
     # --------------------------------------------------------------------------
     # Complex types for paging.
@@ -572,7 +592,7 @@ components:
         effectiveActivationDate: "2024-10-30T16:39:34+01:00"
         payer:
           fiscalCode: "RSSMRA85T10A562S"
-          rtpSpId: "10987654321"
+          rtpSpId: "984500A9EB6B07AC2G71"
 
     Activations:
       description: List of RTP activations.
@@ -586,7 +606,7 @@ components:
           effectiveActivationDate: "2024-10-30T16:39:34+01:00"
           payer:
             fiscalCode: "RSSMRA85T10A562S"
-            rtpSpId: "10987654321"
+            rtpSpId: "984500A9EB6B07AC2G71"
 
     ActivationReq:
       description: |
@@ -601,7 +621,7 @@ components:
       example:
         payer:
           fiscalCode: "RSSMRA85T10A562S"
-          rtpSpId: "10987654321"
+          rtpSpId: "984500A9EB6B07AC2G71"
   
     PageOfActivations:
       description: Page of RTP activations.
@@ -621,7 +641,7 @@ components:
             effectiveActivationDate: "2024-10-30T16:39:34+01:00"
             payer:
               fiscalCode: "RSSMRA85T10A562S"
-              rtpSpId: "10987654321"
+              rtpSpId: "984500A9EB6B07AC2G71"
         page:
           totalElements: 2
           totalPages: 2
@@ -643,7 +663,7 @@ components:
         - rtpSpId
       example:
         fiscalCode: "RSSMRA85T10A562S"
-        rtpSpId: "10987654321"
+        rtpSpId: "984500A9EB6B07AC2G71"
 
   # ============================================================================
   # Request bodies.
@@ -861,4 +881,4 @@ components:
           scopes:
             admin_rtp_activations: Admin RPT activation.
             write_rtp_activations: Create, update or delete RTP activation.
-            read_rtp_activations: Read RTP activation.
+            read_rtp_activations: Read RTP activation.
\ No newline at end of file