diff --git a/app/models.py b/app/models.py
index c32d059..ff0f1f3 100644
--- a/app/models.py
+++ b/app/models.py
@@ -1,10 +1,11 @@
-from sqlalchemy import Column, Integer, String, Float, Date
+from sqlalchemy import Column, Integer, String, Float, Date, ForeignKey
+from sqlalchemy.orm import relationship
 from app.database import Base
 
 class Customer(Base):
     __tablename__ = "customers"
 
-    customer_id = Column(String(20), primary_key=True, index=True)  # IDs are strings now
+    customer_id = Column(String(20), primary_key=True, index=True)
     full_name = Column(String(100), index=True)
     email = Column(String(100), unique=True)
     phone = Column(String(50))
@@ -22,13 +23,35 @@ class Customer(Base):
     credit_score = Column(Integer)
     preferred_contact_method = Column(String(20))
 
+    accounts = relationship("Account", back_populates="customer")
+
+
 class Account(Base):
     __tablename__ = "accounts"
 
-    account_id = Column(String(20), primary_key=True, index=True)  # IDs are strings now
+    account_id = Column(String(20), primary_key=True, index=True)
     account_number = Column(String(20), unique=True, index=True)
-    customer_id = Column(String(20))  # matches Customer.customer_id
+    customer_id = Column(String(20), ForeignKey("customers.customer_id"))
     account_type = Column(String(20))
     open_date = Column(Date)
     balance = Column(Float)
-    branch_id = Column(Integer)
\ No newline at end of file
+    branch_id = Column(Integer)
+
+    customer = relationship("Customer", back_populates="accounts")
+    transactions = relationship("Transaction", back_populates="account")
+
+
+class Transaction(Base):
+    __tablename__ = "transactions"
+
+    transaction_id = Column(String(30), primary_key=True, index=True)
+    account_id = Column(String(20), ForeignKey("accounts.account_id"))
+    branch_id = Column(Integer)
+    transaction_type = Column(String(50))
+    amount = Column(Float)
+    date = Column(Date)
+    balance_after = Column(Float)
+    vendor = Column(String(100))
+    transaction_location = Column(String(100))
+
+    account = relationship("Account", back_populates="transactions")