diff --git a/app/gas-relayer/abi/IdentityGasRelay.json b/app/gas-relayer/abi/IdentityGasRelay.json
index 05cec0c..a83b817 100644
--- a/app/gas-relayer/abi/IdentityGasRelay.json
+++ b/app/gas-relayer/abi/IdentityGasRelay.json
@@ -1 +1 @@
-[{"constant":false,"inputs":[{"name":"_baseToken","type":"address"},{"name":"_to","type":"address"},{"name":"_value","type":"uint256"},{"name":"_data","type":"bytes"},{"name":"_nonce","type":"uint256"},{"name":"_gasPrice","type":"uint256"},{"name":"_gasMinimal","type":"uint256"},{"name":"_gasToken","type":"address"},{"name":"_messageSignatures","type":"bytes"}],"name":"approveAndCallGasRelayed","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_value","type":"uint256"},{"name":"_data","type":"bytes"},{"name":"_nonce","type":"uint256"},{"name":"_gasPrice","type":"uint256"},{"name":"_gasMinimal","type":"uint256"},{"name":"_gasToken","type":"address"},{"name":"_messageSignatures","type":"bytes"}],"name":"callGasRelayed","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"anonymous":false,"inputs":[],"name":"Debug","type":"event"}]
\ No newline at end of file
+[{"constant":false,"inputs":[{"name":"_baseToken","type":"address"},{"name":"_to","type":"address"},{"name":"_value","type":"uint256"},{"name":"_data","type":"bytes"},{"name":"_nonce","type":"uint256"},{"name":"_gasPrice","type":"uint256"},{"name":"_gasLimit","type":"uint256"},{"name":"_gasToken","type":"address"},{"name":"_messageSignatures","type":"bytes"}],"name":"approveAndCallGasRelayed","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":false,"inputs":[{"name":"_to","type":"address"},{"name":"_value","type":"uint256"},{"name":"_data","type":"bytes"},{"name":"_nonce","type":"uint256"},{"name":"_gasPrice","type":"uint256"},{"name":"_gasLimit","type":"uint256"},{"name":"_gasToken","type":"address"},{"name":"_messageSignatures","type":"bytes"}],"name":"callGasRelayed","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"anonymous":false,"inputs":[],"name":"Debug","type":"event"}]
\ No newline at end of file
diff --git a/app/gas-relayer/config/config.json b/app/gas-relayer/config/config.json
index 1a2c578..67fde4f 100644
--- a/app/gas-relayer/config/config.json
+++ b/app/gas-relayer/config/config.json
@@ -1,8 +1,9 @@
 {
     "blockchain": {
         "account": "0x9e14016ba37b23498885864053fded5226161a3a",
-        "rpcHost": "localhost",
-        "rpcPort": 8545
+        "protocol": "ws",
+        "host": "localhost",
+        "port": 8545
     },
     
     "whisper": {
@@ -32,7 +33,7 @@
     "contracts":{
         "IdentityGasRelay": {
             "isIdentity": true,
-            "factoryAddress": "0x96f0811c6484c59c2674da1f64e725c01d82c1b5",
+            "factoryAddress": "0x18f71378f4735b35e01eb71afcc66df090eccea7",
             "abiFile": "../abi/IdentityGasRelay.json",
             "allowedFunctions": [
                 { 
diff --git a/app/gas-relayer/package.json b/app/gas-relayer/package.json
index e587f0e..b7d36b9 100644
--- a/app/gas-relayer/package.json
+++ b/app/gas-relayer/package.json
@@ -10,6 +10,7 @@
   "license": "ISC",
   "dependencies": {
     "daemonize2": "^0.4.2",
+    "ganache-cli": "^6.1.0",
     "md5": "^2.2.1",
     "web3": "^1.0.0-beta.33"
   }
diff --git a/app/gas-relayer/src/service.js b/app/gas-relayer/src/service.js
index b7f9ce9..e6d4f23 100644
--- a/app/gas-relayer/src/service.js
+++ b/app/gas-relayer/src/service.js
@@ -2,6 +2,7 @@ const md5 = require('md5');
 const Web3 = require('web3');
 const config = require('../config/config.json');
 const web3 = new Web3(`${config.whisper.protocol}://${config.whisper.host}:${config.whisper.port}`);
+var ganache = require("ganache-cli");
 
 const erc20ABI = require('../abi/ERC20.json');
 
@@ -64,7 +65,6 @@ for(let contractName in config.contracts){
   }
 }
 
-
 // Setting up Whisper options
 const shhOptions = {
   ttl: config.whisper.ttl,
@@ -169,7 +169,7 @@ const processMessages = async function(error, message, subscription){
       Token.options.address = params[contract.allowedFunctions[functionName].gasToken];
       balance = new web3.utils.BN(await Token.methods.balanceOf(address).call());  
     }
-
+    
     // Determine if enough balance for baseToken
     if(contract.allowedFunctions[functionName].isToken){
       const Token = new web3.eth.Contract(erc20ABI);
@@ -179,21 +179,38 @@ const processMessages = async function(error, message, subscription){
         return reply("Not enough balance", message);
       }   
     }
-
+    
     // Obtain factor
     let factor;
     if(contract.allowedFunctions[functionName].isToken){
-      factor = config.tokens[tokenAddress].pricePlugin.getFactor();
+      factor =web3.utils.toBN(config.tokens[tokenAddress].pricePlugin.getFactor());
     } else {
-      factor = 1;
+      factor = web3.utils.toBN(1);
     }
-
+    
     const balanceInETH = balance.div(factor);
     const gasLimitInETH = gasLimit.div(factor);
-    if(balanceInETH.lt(web3.utils.toBN(gasPrice.mul(gasLimit)))){
+
+    if(balanceInETH.lt(web3.utils.toBN(gasPrice.mul(gasLimit)))) {
       return reply("Not enough balance", message);
     }
+    
+    // Estimate costs
+    const web3Sim = new Web3(ganache.provider({fork: `${config.blockchain.protocol}://${config.blockchain.host}:${config.blockchain.port}`}));
+    const simAccounts = await web3.eth.getAccounts();
+    let simulatedReceipt = await web3.eth.sendTransaction({
+      from: simAccounts[0],
+      to: address,
+      value: 0,
+      data: payload
+    });
+    const estimatedGas = web3.utils.toBN(simulatedReceipt.gasUsed);
+    
+    if(gasLimit.lt(estimatedGas)) {
+      return reply("Gas limit below estimated gas", message);
+    }
 
+    
     web3.eth.sendTransaction({
         from: config.blockchain.account,
         to: address,
diff --git a/app/gas-relayer/test/sampleContracts.sol b/app/gas-relayer/test/sampleContracts.sol
index 178cb28..eeca5dd 100644
--- a/app/gas-relayer/test/sampleContracts.sol
+++ b/app/gas-relayer/test/sampleContracts.sol
@@ -10,7 +10,7 @@ contract TestIdentityGasRelay {
         bytes _data,
         uint _nonce,
         uint _gasPrice,
-        uint _gasMinimal,
+        uint _gasLimit,
         address _gasToken,
         bytes _messageSignatures
     ) external {
@@ -23,7 +23,7 @@ contract TestIdentityGasRelay {
         bytes _data,
         uint _nonce,
         uint _gasPrice,
-        uint _gasMinimal,
+        uint _gasLimit,
         address _gasToken, 
         bytes _messageSignatures
     ) external {