diff --git a/contracts/Bank.sol b/contracts/Bank.sol
new file mode 100644
index 0000000..8279964
--- /dev/null
+++ b/contracts/Bank.sol
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: MIT
+pragma solidity >=0.4.22 <0.9.0;
+import "@openzeppelin/contracts/utils/Counters.sol";
+import "./SoulboundToken.sol";
+
+contract Bank {
+    using Counters for Counters.Counter;
+    Counters.Counter private id_counter;
+
+	SoulboundToken SBT;
+	address owner;
+	mapping(address => uint) arrears;
+	mapping(address => uint) SBTNumbers;
+
+	constructor(address SBT_addr) {
+		SBT = SoulboundToken(SBT_addr);
+	}
+
+    modifier onlyBank {
+        require(msg.sender == owner, "Only the owner can access this function.");
+        _;
+    }
+
+	function register(uint number) public {
+		uint target = SBT.getAccountNumber(msg.sender);
+		require(target == number, "This is not your SBT number.");
+		SBTNumbers[msg.sender] = target;
+	}
+}
diff --git a/contracts/SoulboundToken.sol b/contracts/SoulboundToken.sol
index d6daf64..86565e7 100644
--- a/contracts/SoulboundToken.sol
+++ b/contracts/SoulboundToken.sol
@@ -17,6 +17,7 @@ contract SoulboundToken is ERC721, Ownable {
 
     mapping(address => bool) private isReliableBank;
     mapping(address => Certificate[]) private certificates;
+    mapping(address => uint) private address_to_number;
 
     event Borrow(address client, address bank, uint id, uint amount);
     event Repay(address client, address bank, uint id, uint amount, bool finish);
@@ -28,6 +29,7 @@ contract SoulboundToken is ERC721, Ownable {
         _tokenIds.increment();
         uint256 newItemId = _tokenIds.current();
         _mint(player, newItemId);
+        address_to_number[player] = newItemId;
 
         return newItemId;
     }
@@ -103,4 +105,8 @@ contract SoulboundToken is ERC721, Ownable {
     function listCertificate(address client) public view onlyBank returns (Certificate[] memory){
         return certificates[client];
     }
+
+    function getAccountNumber(address client) public view onlyBank returns (uint) {
+        return address_to_number[client];
+    }
 }
\ No newline at end of file
diff --git a/migrations/1685866933_migrate_credit_system.js b/migrations/1685866933_migrate_credit_system.js
index 65377c2..b62bd00 100644
--- a/migrations/1685866933_migrate_credit_system.js
+++ b/migrations/1685866933_migrate_credit_system.js
@@ -1,6 +1,11 @@
-var MyNFT = artifacts.require("SoulboundToken");
+var SBT = artifacts.require("SoulboundToken");
+var Bank = artifacts.require("Bank");
 
 module.exports = function(_deployer) {
 	// Use deployer to state migration tasks.
-	_deployer.deploy(MyNFT, );
+	_deployer.deploy(SBT).then((SBT_instance) => {
+		return _deployer.deploy(Bank, SBT_instance.address).then((Bank_instance) => {
+			return SBT_instance.addReliableBank(Bank_instance.address);
+		})
+	})
 };