diff --git a/src/clifinance/domain/expense/model.py b/src/clifinance/domain/expense/model.py
index 2cd279b..c94ae50 100644
--- a/src/clifinance/domain/expense/model.py
+++ b/src/clifinance/domain/expense/model.py
@@ -53,22 +53,3 @@ class Expense(DomainEntity[ExpenseId]):
             amount=ExpenseAmount(amount),
             description=ExpenseDescription(description),
         )
-
-    def to_json(self) -> dict:
-        return {
-            "id": self.id.value,
-            "type": self.type.value,
-            "date": self.date.isoformat(),
-            "amount": self.amount.value,
-            "description": self.description.value,
-        }
-
-    @staticmethod
-    def from_json(data: dict) -> "Expense":
-        return Expense(
-            id=ExpenseId(data["id"]),
-            type=ExpenseType(data["type"]),
-            date=ExpenseDate.from_isoformat(data["date"]),
-            amount=ExpenseAmount(data["amount"]),
-            description=ExpenseDescription(data["description"]),
-        )
diff --git a/src/clifinance/infrastructure/persistence/json_driver.py b/src/clifinance/infrastructure/persistence/json_driver.py
index af0a665..3087a88 100644
--- a/src/clifinance/infrastructure/persistence/json_driver.py
+++ b/src/clifinance/infrastructure/persistence/json_driver.py
@@ -1,10 +1,14 @@
 import json
 
 from clifinance.domain.expense.model import Expense
+from clifinance.infrastructure.persistence.mappers.expense import (
+    expense_from_json,
+    expense_to_json,
+)
 
 
 class JsonFileDriver:
-    def read(self):
+    def read(self) -> list[Expense]:
         try:
             with open("./app_data.json") as f:
                 data = json.load(f)
@@ -15,12 +19,12 @@ class JsonFileDriver:
         except json.JSONDecodeError:
             return list()
 
-    def write(self, data: list[Expense]):
+    def write(self, data: list[Expense]) -> None:
         with open("./app_data.json", "w") as f:
             json.dump(self.__data_to_json(data), f)
 
-    def __data_to_json(self, data: list[Expense]):
-        return [x.to_json() for x in data]
+    def __data_to_json(self, data: list[Expense]) -> list[dict]:
+        return [expense_to_json(x) for x in data]
 
-    def __data_from_json(self, data: list[dict]):
-        return [Expense.from_json(x) for x in data]
+    def __data_from_json(self, data: list[dict]) -> list[Expense]:
+        return [expense_from_json(x) for x in data]
diff --git a/src/clifinance/infrastructure/persistence/mappers/__init__.py b/src/clifinance/infrastructure/persistence/mappers/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/src/clifinance/infrastructure/persistence/mappers/expense.py b/src/clifinance/infrastructure/persistence/mappers/expense.py
new file mode 100644
index 0000000..5f8dcb7
--- /dev/null
+++ b/src/clifinance/infrastructure/persistence/mappers/expense.py
@@ -0,0 +1,28 @@
+from clifinance.domain.expense.model import (
+    Expense,
+    ExpenseAmount,
+    ExpenseDate,
+    ExpenseDescription,
+    ExpenseId,
+    ExpenseType,
+)
+
+
+def expense_to_json(expense: Expense):
+    return {
+        "id": expense.id.value,
+        "description": expense.description.value,
+        "amount": expense.amount.value,
+        "date": expense.date,
+        "type": expense.type.value,
+    }
+
+
+def expense_from_json(data: dict):
+    return Expense(
+        id=ExpenseId(data["id"]),
+        description=ExpenseDescription(data["description"]),
+        amount=ExpenseAmount(data["amount"]),
+        date=ExpenseDate(data["date"]),
+        type=ExpenseType(data["type"]),
+    )
diff --git a/src/clifinance/infrastructure/session.py b/src/clifinance/infrastructure/session.py
index 691416d..42a4450 100644
--- a/src/clifinance/infrastructure/session.py
+++ b/src/clifinance/infrastructure/session.py
@@ -38,11 +38,6 @@ class JsonFileSession(Session):
         self.data = self.driver.read()
 
     def add(self, expense: Expense) -> None:
-        # if not self.data:
-        #     last_id = -1
-        # else:
-        #     last_id = max({x.id for x in self.data if x.id is not None})
-        #
         self.__dirty_new.append(expense)
 
     def update(self, expense: Expense) -> None: