diff --git a/controllers_v2/finstitutions/payments/base.py b/controllers_v2/finstitutions/payments/base.py
index 324c3df..fb3ee47 100644
--- a/controllers_v2/finstitutions/payments/base.py
+++ b/controllers_v2/finstitutions/payments/base.py
@@ -343,7 +343,7 @@ class PaymentsController(CoreAuthTokenController, ABC):
                 payment.metadata.inAccount,  # ................................... p_in_account
                 payment.metadata.idUser,  # ...................................... p_user_id
                 payment.metadata.documentUrl,  # ................................. p_document_url
-                payment.metadata.againstReference  # ............................. p_notes
+                json.to_string(payment.metadata.againstReference)  # ............. p_notes
             ),
             retry_count = 1,
             backoff_seconds = 0.5,
@@ -356,6 +356,25 @@ class PaymentsController(CoreAuthTokenController, ABC):
         if sql_json["status"] == 1: return True
         else: return False
 
+    async def add_sales_transaction(
+            self,
+            sql_conn: AsyncMySQL,
+            mongo_data_conn: AsyncMongo,
+            payment: CorePaymentModel,
+            session_token: str = None
+    ) -> bool:
+
+        """
+        ???
+        :param sql_conn: The database connection to use to perform this activity.
+        :param mongo_data_conn: The database connection to use to perform this activity.
+        :param payment: The record of the payment whose details need to be added as a receipt.
+        :param session_token: The session token of the user to identify whose request caused this receipt update.
+        :return: True is the receipt was added, else False.
+        """
+
+        pass
+
     async def add_event_by_payment_id(
             self,
             mongo_data_conn: AsyncMongo,
diff --git a/models/api/finstitutions/payments/request.py b/models/api/finstitutions/payments/request.py
index 4b8f232..62f3f16 100644
--- a/models/api/finstitutions/payments/request.py
+++ b/models/api/finstitutions/payments/request.py
@@ -40,6 +40,7 @@ from pydantic import BaseModel, Field, field_validator, PastDatetime
 from typing import Optional, Literal, Union, List, Any
 
 # My utils:
+from utils_v2.string import json
 from utils_v2.string import regex
 
 # To work with MongoDB:
@@ -117,7 +118,7 @@ class PaymentRequestMetadata(BaseModel):
     idClient: int = Field(frozen = True)
     inAccount: int = Field(frozen = True)
     reference: str | None = Field(frozen = True, default = None, validate_default = True)
-    againstReference: str | None = Field(frozen = True, default = None, validate_default = True)
+    againstReference: dict | None = Field(frozen = True, default = None, validate_default = True)
     documentUrl: str | None = Field(frozen = False, default = None, validate_default = True)
 
     # ┏┓    ┏•
@@ -137,9 +138,10 @@ class PaymentRequestMetadata(BaseModel):
         if not value: value = "On Account"
         return value
 
-    @field_validator("againstReference")
+    @field_validator("againstReference", mode = "before")
     def validate_against_reference(cls, value):
         if not value: value = None
+        if isinstance(value, str): value = json.from_string(value)
         return value
 
     @field_validator("documentUrl")
diff --git a/models/core/payment.py b/models/core/payment.py
index 99b4a6f..22f8467 100644
--- a/models/core/payment.py
+++ b/models/core/payment.py
@@ -147,7 +147,7 @@ class PaymentMetadata(BaseModel):
     idClient: int | None = Field(frozen = True, default = None, validate_default = True)
     inAccount: int | None = Field(frozen = True, default = None, validate_default = True)
     reference: str | None = Field(frozen = True, default = None, validate_default = True)
-    againstReference: str | None = Field(frozen = True, default = None, validate_default = True)
+    againstReference: dict | None = Field(frozen = True, default = None, validate_default = True)
     documentUrl: str | None = Field(frozen = False, default = None, validate_default = True)
 
     # ┏┓    ┏•
@@ -167,9 +167,10 @@ class PaymentMetadata(BaseModel):
         if not value: value = "On Account"
         return value
 
-    @field_validator("againstReference")
+    @field_validator("againstReference", mode = "before")
     def validate_against_reference(cls, value):
         if not value: value = None
+        if isinstance(value, str): value = json.from_string(value)
         return value
 
     @field_validator("documentUrl")