Whenever someone buys a smart-contract the amount (in Wei) get stored in SC(Smart Contract) address(this) += msg.value.

Now I am trying to create a function to redeem the balance of the SC

function redeemInvTokens(uint256 _amount) public returns(bool){
    require(_amount <= amount, "you cannot redeem the more tokens");
    balanceOf[msg.sender] -= _amount;
    msg.sender.call.value(address(this).balance - (address(this).balance - _amount))("Transferred ether to financier");
    return true;

but its not transferring any amount to the msg.sender.

How to transfer the specific amount to the msg.sender? so I don't have to use address(this).balance - (address(this).balanace - _amount).

  • 1
    "so I don't have to use address(this).balance - (address(this).balanace - _amount)"??? This expression is equivalent to _amount, what brought you to the conclusion that you need to use it in order to transfer the specific amount to the sender? You can simply do msg.sender.transfer(_amount). Jan 21, 2020 at 8:28
  • Also, what is amount in require(_amount <= amount, ...)? You should post a working example. This symbol (amount) is not defined anywhere in your code. Jan 21, 2020 at 8:30
  • msg.sender.call.value(_amount)() it is not transfering any amount to msg.sender so i used msg.sender.call.value(address(this).balance)(). but, again i want to send specific amount to msg.sender thats why that calculation to determine.
    – iamsujit
    Jan 21, 2020 at 8:48
  • x - (x - y) == y!!! Jan 21, 2020 at 8:50
  • And on top of that of that, why not simply do msg.sender.transfer(_amount)? Jan 21, 2020 at 8:51

2 Answers 2


You can use call with gas estimation.

for example,


In your case:

uint256 transferableAmount = address(this).balance -(address(this).balance - _amount);
  • but isn't this method should be avoided after Istanbul update ethereum.stackexchange.com/a/19343/50405
    – iamsujit
    Jan 21, 2020 at 6:25
  • Yes. but you don't mention the exact error msg or transaction hash of transferred amount so. Don't worry I have edited the answer. pls check and let me know. Jan 21, 2020 at 6:32

Here is the sample example

    // SPDX-License-Identifier: GPL-3.0
        pragma solidity >=0.7.0 <0.9.0;
         * @title SimpleVault
         * @dev Store & retrieve Funds from the contract
         * @custom:dev-run-script ./scripts/deploy_with_ethers.ts
        contract SimpleVault {
            address payable owner;
            constructor () payable {
                owner = payable(msg.sender);
            function withdraw() public {
                   payable (msg.sender).transfer(getBalance());     // Transfer to msg.sender
                // payable (0xAb8483F64d9C6d1EcF9b849Ae677dD3315835cb2).transfer(getBalance());  // Transfer to a specific address
               (bool success, ) = address(0xAb8483F64d9C6d1EcF9b849Ae677dD3315835cb2).call{value:getBalance()}("");
            require(success, "Transfer failed."); 
            function getBalance() public view returns (uint) {
               return address(this).balance;

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