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+<pre>
+  NEP: 22
+  Title: Contract Update Function
+  Author: Owen Zhang <zhangzhihong@ngd.neo.org>, Fernando Díaz Toledano <shargon@gmail.com>, Erik Zhang <erik@neo.org>, Roman Khimov <roman@nspcc.ru>
+  Type: Standard
+  Status: Accepted
+  Created: 2021-04-19
+</pre>
+
+
+==Abstract==
+
+This proposal outlines a standard for the NEO blockchain that will provide systems with a generalized interaction mechanism for smart contract update.
+
+==Motivation==
+
+As the NEO blockchain scales, Smart Contract Update will become increasingly important. We need standize <code>update</code> method in contract to callback native <code>ContractManagement</code> correctly.
+
+==Specification==
+
+Neo N3 has a native <code>ContractManagement</code> contract that is used for contract deployment and update via <code>deploy</code> and <code>update</code> methods of it. After settling with the new NEF and manifest both of them will invoke a special <code>_deploy</code> method if it's implemented by the contract. More details in [NEP-29](https://github.com/neo-project/proposals/blob/master/nep-29.mediawiki)
+
+===Methods===
+
+====update====
+
+<pre>
+{
+  "name": "update",
+  "safe": false,
+  "parameters": [
+    {
+      "name": "nefFile",
+      "type": "ByteArray"
+    },
+    {
+      "name": "manifest",
+      "type": "ByteArray"
+    },
+    {
+      "name": "data",
+      "type": "Any"
+    }
+  ],
+  "returntype": "Void"
+}
+</pre>
+
+This method will will callback <code>Update</code> method in native <code>ContractManagement</code> contract. It will update contract state if it's exectued successfully.
+
+Updating a smart contract MUST have <code>nefFile</code> or <code>manifest.json</code>. If just update one of them at a time is OK, another SHOULD be set as null. It will be passed to <code>_deploy</code>.
+
+The parameter <code>data</code> can be any type of supported parameters for contract-specific purpose. For example some kinds of json parameters can be put into data for specific check.
+
+This function SHOULD check whether the <code>signer</code> address equals the <code>owner</code> hash of contract. This function SHOULD use the SYSCALL <code>Neo.Runtime.CheckWitness</code> to verify the <code>signer</code>. Details has been explained in [NEP-30](https://github.com/superboyiii/proposals/blob/upgrade-standard/nep-30.mediawiki).
+
+===References===
+
+https://github.com/neo-project/proposals/blob/master/nep-29.mediawiki
+
+https://github.com/neo-project/proposals/blob/master/nep-30.mediawiki
+
+===Implementation===
+
+* C#: https://github.com/neo-project/neo-devpack-dotnet/blob/003a50095efe88f63f518a0c989921be086409f3/examples/Example.SmartContract.NEP17/SampleNep17Token.cs#L130
+
+* Go: https://github.com/nspcc-dev/neofs-contract/blob/99fb86c35a48ed12017423aa4fee13f7d07fa4c0/contracts/proxy/contract.go#L33