diff --git a/README.md b/README.md
index cab3c08..76507d5 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,4 @@
+[![Review Assignment Due Date](https://classroom.github.com/assets/deadline-readme-button-22041afd0340ce965d47ae6ef1cefeee28c7c493a6346c4f15d667ab976d596c.svg)](https://classroom.github.com/a/W3nV4mdD)
 # Banking management
 
 ## Overview
diff --git a/src/index.ts b/src/index.ts
index 3972b63..ff5ffa5 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,5 +1,4 @@
-import isEqual from '@/is-equal';
-
-export default function isEqualChecker(obj1, obj2) {
-  return isEqual(obj1, obj2);
-}
\ No newline at end of file
+export { default as Bank } from '@/models/bank';
+export { default as User } from '@/models/user';
+export { default as BankAccount } from '@/models/bank-account';
+export { default as TransactionService } from '@/services/TransactionService';
diff --git a/src/models/bank-account.ts b/src/models/bank-account.ts
new file mode 100644
index 0000000..32049ed
--- /dev/null
+++ b/src/models/bank-account.ts
@@ -0,0 +1,62 @@
+import { genId } from '@/utils/id';
+
+export default class BankAccount {
+  private id: string;
+  private balance: number;
+  private bankId: string;
+  private ownerId: string | null = null;
+  private allowsNegative: boolean;
+
+  constructor(bankId: string, initialBalance = 0, allowsNegative = false) {
+    this.id = genId('acct');
+    this.bankId = bankId;
+    this.balance = initialBalance;
+    this.allowsNegative = allowsNegative;
+  }
+
+  static create(bankId: string, initialBalance = 0, allowsNegative = false) {
+    return new BankAccount(bankId, initialBalance, allowsNegative);
+  }
+
+  getId(): string {
+    return this.id;
+  }
+
+  getBalance(): number {
+    return this.balance;
+  }
+
+  getBankId(): string {
+    return this.bankId;
+  }
+
+  getOwnerId(): string | null {
+    return this.ownerId;
+  }
+
+  setOwner(userId: string) {
+    this.ownerId = userId;
+  }
+
+  deposit(amount: number) {
+    if (amount <= 0) throw new Error('Deposit must be positive');
+    this.balance += amount;
+  }
+
+  canWithdraw(amount: number): boolean {
+    if (amount <= 0) return false;
+    if (this.allowsNegative) return true;
+    return this.balance - amount >= 0;
+  }
+
+  withdraw(amount: number) {
+    if (amount <= 0) throw new Error('Withdraw must be positive');
+    if (!this.canWithdraw(amount)) throw new Error('Insufficient funds');
+    this.balance -= amount;
+  }
+
+  forceWithdraw(amount: number) {
+    if (amount <= 0) throw new Error('Withdraw must be positive');
+    this.balance -= amount;
+  }
+}
diff --git a/src/models/bank.ts b/src/models/bank.ts
new file mode 100644
index 0000000..d541336
--- /dev/null
+++ b/src/models/bank.ts
@@ -0,0 +1,122 @@
+import { genId } from '@/utils/id';
+import BankAccount from '@/models/bank-account';
+import { registerBank, registerAccount, getAccountById, getUserById, getBankById } from '@/stores/Registry';
+
+export default class Bank {
+  private id: string;
+  private accounts: Map<string, BankAccount> = new Map();
+  private allowsNegativeBalance: boolean;
+
+  private constructor(allowsNegativeBalance = false) {
+    this.id = genId('bank');
+    this.allowsNegativeBalance = allowsNegativeBalance;
+    registerBank(this.id, this);
+  }
+
+  static create(allowsNegativeBalance = false): Bank {
+    return new Bank(allowsNegativeBalance);
+  }
+
+  getId(): string {
+    return this.id;
+  }
+
+  createAccount(initialBalance = 0): BankAccount {
+    const acct = BankAccount.create(this.id, initialBalance, this.allowsNegativeBalance);
+    this.accounts.set(acct.getId(), acct);
+    registerAccount(acct.getId(), acct);
+    return acct;
+  }
+
+  getAccount(accountId: string): BankAccount {
+    const acct = this.accounts.get(accountId);
+    if (!acct) throw new Error('Account not found');
+    return acct;
+  }
+
+  send(fromUserId: string, toUserId: string, amount: number, toBankId?: string) {
+    if (amount <= 0) throw new Error('Transfer amount must be positive');
+
+    const fromUser = getUserById(fromUserId);
+    const toUser = getUserById(toUserId);
+    if (!fromUser || !toUser) throw new Error('User not found');
+
+    const destBank = toBankId ? getBankById(toBankId) : this;
+    if (!destBank) throw new Error('Destination bank not found');
+
+    const toAcctId = toUser.getAccountIds().find(id => {
+      const acct = getAccountById(id);
+      return acct && (acct as any).getBankId?.() === destBank.getId();
+    });
+
+    if (!toAcctId) throw new Error('Destination account not found for user in destination bank');
+
+    const toAcct = getAccountById(toAcctId)!;
+
+    const fromAcctIds = fromUser.getAccountIds().filter(id => {
+      const acct = getAccountById(id);
+      return acct && (acct as any).getBankId?.() === this.getId();
+    });
+
+    if (fromAcctIds.length === 0) throw new Error('Source account not found for user in this bank');
+
+    const primaryAcct = getAccountById(fromAcctIds[0])!;
+
+    const sameBankDestination = destBank.getId() === this.getId();
+
+    if (primaryAcct.canWithdraw(amount)) {
+      primaryAcct.withdraw(amount);
+      (toAcct as any).deposit(amount);
+      (fromUser as any).addAccountIdFront(primaryAcct.getId());
+      (toUser as any).addAccountIdFront(toAcct.getId());
+      return;
+    }
+
+    if (this.allowsNegativeBalance) {
+      (primaryAcct as any).forceWithdraw(amount);
+      (toAcct as any).deposit(amount);
+      (fromUser as any).addAccountIdFront(primaryAcct.getId());
+      (toUser as any).addAccountIdFront(toAcct.getId());
+      return;
+    }
+
+    if (sameBankDestination) {
+      let totalAvailable = 0;
+      const acctObjs = fromAcctIds.map(id => getAccountById(id)!);
+      for (const a of acctObjs) {
+        totalAvailable += Math.max(0, (a as any).getBalance());
+      }
+      if (totalAvailable < amount) {
+        throw new Error('Insufficient funds');
+      }
+
+      let remaining = amount;
+      const deltas: Array<{ acct: any; withdrawAmt: number }> = [];
+
+      for (const a of acctObjs) {
+        if (remaining <= 0) break;
+        const available = Math.max(0, a.getBalance());
+        const take = Math.min(available, remaining);
+        if (take > 0) {
+          deltas.push({ acct: a, withdrawAmt: take });
+          remaining -= take;
+        }
+      }
+
+      if (remaining > 0) {
+        throw new Error('Insufficient funds');
+      }
+
+      for (const d of deltas) {
+        d.acct.withdraw(d.withdrawAmt);
+        (fromUser as any).addAccountIdFront(d.acct.getId());
+      }
+
+      (toAcct as any).deposit(amount);
+      (toUser as any).addAccountIdFront(toAcct.getId());
+      return;
+    }
+
+    throw new Error('Insufficient funds');
+  }
+}
diff --git a/src/models/user.ts b/src/models/user.ts
new file mode 100644
index 0000000..364aee2
--- /dev/null
+++ b/src/models/user.ts
@@ -0,0 +1,51 @@
+import { genId } from '@/utils/id';
+import { registerUser, getAccountById } from '@/stores/Registry';
+
+export default class User {
+  private id: string;
+  private name: string;
+  private accountIds: string[] = [];
+
+  private constructor(name: string, accountIds: string[]) {
+    this.id = genId('user');
+    this.name = name;
+    this.accountIds = [...accountIds];
+
+    for (const acctId of accountIds) {
+      const acct = getAccountById(acctId);
+      if (acct) {
+        try {
+          (acct as any).setOwner?.(this.id);
+        } catch {
+
+        }
+      }
+    }
+
+    registerUser(this.id, this);
+  }
+
+  static create(name: string, accountIds: string[]) {
+    return new User(name, accountIds);
+  }
+
+  getId(): string {
+    return this.id;
+  }
+
+  getName(): string {
+    return this.name;
+  }
+
+  getAccountIds(): string[] {
+    return [...this.accountIds];
+  }
+
+  addAccountIdFront(acctId: string) {
+    this.accountIds = [acctId, ...this.accountIds.filter(id => id !== acctId)];
+  }
+
+  addAccountIdBack(acctId: string) {
+    if (!this.accountIds.includes(acctId)) this.accountIds.push(acctId);
+  }
+}
diff --git a/src/services/GlobalRegistry.ts b/src/services/GlobalRegistry.ts
new file mode 100644
index 0000000..b73bab6
--- /dev/null
+++ b/src/services/GlobalRegistry.ts
@@ -0,0 +1,39 @@
+import type Bank from '@/models/bank';
+import type User from '@/models/user';
+import type BankAccount from '@/models/bank-account';
+
+const banks: Map<string, Bank> = new Map();
+const users: Map<string, User> = new Map();
+const accounts: Map<string, BankAccount> = new Map();
+
+export default class GlobalRegistry {
+  static registerBank(bank: Bank) {
+    banks.set(bank.getId(), bank);
+  }
+
+  static getBank(id: string): Bank | undefined {
+    return banks.get(id);
+  }
+
+  static registerUser(user: User) {
+    users.set(user.getId(), user);
+  }
+
+  static getUser(id: string): User | undefined {
+    return users.get(id);
+  }
+
+  static registerAccount(account: BankAccount) {
+    accounts.set(account.getId(), account);
+  }
+
+  static getAccount(id: string): BankAccount | undefined {
+    return accounts.get(id);
+  }
+
+  static clear() {
+    banks.clear();
+    users.clear();
+    accounts.clear();
+  }
+}
diff --git a/src/services/TransactionService.ts b/src/services/TransactionService.ts
new file mode 100644
index 0000000..8c185c2
--- /dev/null
+++ b/src/services/TransactionService.ts
@@ -0,0 +1,5 @@
+export default class TransactionService {
+  static create() {
+    return new TransactionService();
+  }
+}
diff --git a/src/stores/Registry.ts b/src/stores/Registry.ts
new file mode 100644
index 0000000..ab551f9
--- /dev/null
+++ b/src/stores/Registry.ts
@@ -0,0 +1,35 @@
+import type BankAccount from '@/models/bank-account';
+import type Bank from '@/models/bank';
+import type User from '@/models/user';
+
+type BankMap = Map<string, Bank>;
+type AccountMap = Map<string, BankAccount>;
+type UserMap = Map<string, User>;
+
+const banks: BankMap = new Map();
+const accounts: AccountMap = new Map();
+const users: UserMap = new Map();
+
+export function registerBank(id: string, bank: Bank) {
+  banks.set(id, bank);
+}
+
+export function getBankById(id: string): Bank | undefined {
+  return banks.get(id);
+}
+
+export function registerAccount(id: string, account: BankAccount) {
+  accounts.set(id, account);
+}
+
+export function getAccountById(id: string): BankAccount | undefined {
+  return accounts.get(id);
+}
+
+export function registerUser(id: string, user: User) {
+  users.set(id, user);
+}
+
+export function getUserById(id: string): User | undefined {
+  return users.get(id);
+}
diff --git a/src/utils/id.ts b/src/utils/id.ts
new file mode 100644
index 0000000..bebfe40
--- /dev/null
+++ b/src/utils/id.ts
@@ -0,0 +1,4 @@
+let counter = 1;
+export function genId(prefix = 'id'): string {
+  return `${prefix}-${counter++}`;
+}