diff --git a/backend/src/main/resources/db/migration/V12__backfill_user_accounts.sql b/backend/src/main/resources/db/migration/V12__backfill_user_accounts.sql
new file mode 100644
index 00000000..4af69669
--- /dev/null
+++ b/backend/src/main/resources/db/migration/V12__backfill_user_accounts.sql
@@ -0,0 +1,91 @@
+INSERT INTO users (username, password, email, fullName, phone, role, active, tokenVersion)
+SELECT
+    CONCAT('customer_', c.customerId) AS username,
+    '$2a$10$mE0D/HrnCuqFeEqMy0NJwuy2jkoRYjQ7GrKcc/7QQ0r2AqnZTvyGq' AS password,
+    CASE
+        WHEN c.email IS NOT NULL
+         AND c.email <> ''
+         AND (SELECT COUNT(*) FROM customer c2 WHERE c2.email = c.email) = 1
+         AND NOT EXISTS (SELECT 1 FROM employee e2 WHERE e2.email = c.email)
+         AND NOT EXISTS (SELECT 1 FROM users u WHERE u.email = c.email)
+        THEN c.email
+        ELSE CONCAT('customer_', c.customerId, '@petshop.local')
+    END AS email,
+    CONCAT(c.firstName, ' ', c.lastName) AS fullName,
+    CONCAT('200-000-', LPAD(c.customerId, 4, '0')) AS phone,
+    'CUSTOMER' AS role,
+    FALSE AS active,
+    0 AS tokenVersion
+FROM customer c
+WHERE c.user_id IS NULL
+  AND NOT EXISTS (
+      SELECT 1
+      FROM users u
+      WHERE u.username = CONCAT('customer_', c.customerId)
+  );
+
+INSERT INTO users (username, password, email, fullName, phone, role, active, tokenVersion)
+SELECT
+    CONCAT('employee_', e.employeeId) AS username,
+    '$2a$10$mE0D/HrnCuqFeEqMy0NJwuy2jkoRYjQ7GrKcc/7QQ0r2AqnZTvyGq' AS password,
+    CASE
+        WHEN e.email IS NOT NULL
+         AND e.email <> ''
+         AND (SELECT COUNT(*) FROM employee e2 WHERE e2.email = e.email) = 1
+         AND NOT EXISTS (SELECT 1 FROM customer c2 WHERE c2.email = e.email)
+         AND NOT EXISTS (SELECT 1 FROM users u WHERE u.email = e.email)
+        THEN e.email
+        ELSE CONCAT('employee_', e.employeeId, '@petshop.local')
+    END AS email,
+    CONCAT(e.firstName, ' ', e.lastName) AS fullName,
+    CONCAT('300-000-', LPAD(e.employeeId, 4, '0')) AS phone,
+    CASE
+        WHEN UPPER(e.role) = 'MANAGER' THEN 'ADMIN'
+        ELSE 'STAFF'
+    END AS role,
+    FALSE AS active,
+    0 AS tokenVersion
+FROM employee e
+WHERE e.user_id IS NULL
+  AND NOT EXISTS (
+      SELECT 1
+      FROM users u
+      WHERE u.username = CONCAT('employee_', e.employeeId)
+  );
+
+UPDATE customer c
+JOIN users u ON u.username = CONCAT('customer_', c.customerId)
+   AND u.role = 'CUSTOMER'
+SET c.user_id = u.id
+WHERE c.user_id IS NULL;
+
+UPDATE employee e
+JOIN users u ON u.username = CONCAT('employee_', e.employeeId)
+   AND u.role IN ('STAFF', 'ADMIN')
+SET e.user_id = u.id
+WHERE e.user_id IS NULL;
+
+UPDATE users
+SET
+    fullName = CASE
+        WHEN fullName IS NULL OR fullName = '' THEN username
+        ELSE fullName
+    END,
+    email = CASE
+        WHEN email IS NULL OR email = '' THEN CONCAT(username, '@petshop.local')
+        ELSE email
+    END,
+    phone = CASE
+        WHEN phone IS NULL OR phone = '' THEN CONCAT('000-000-', LPAD(id, 4, '0'))
+        ELSE phone
+    END,
+    active = COALESCE(active, TRUE),
+    tokenVersion = COALESCE(tokenVersion, 0)
+WHERE fullName IS NULL
+   OR fullName = ''
+   OR email IS NULL
+   OR email = ''
+   OR phone IS NULL
+   OR phone = ''
+   OR active IS NULL
+   OR tokenVersion IS NULL;
diff --git a/backend/src/main/resources/db/migration/V13__remove_debit_payment_method.sql b/backend/src/main/resources/db/migration/V13__remove_debit_payment_method.sql
new file mode 100644
index 00000000..874b0205
--- /dev/null
+++ b/backend/src/main/resources/db/migration/V13__remove_debit_payment_method.sql
@@ -0,0 +1,3 @@
+UPDATE sale
+SET paymentMethod = 'Card'
+WHERE LOWER(paymentMethod) = 'debit';