How to drain account with Taquito?

Question

I have 9.9 tezos on my address tz2B35M8eHC6FhAVsQrtp8EBPri4H73w7W7C. I want to send all of it to another address tz1i4ezL2FZ1kZ8oqEY8n6wCr2eGRJPC4xin which has never been used and is thus empty. For this I need to make an estimate to get the storage limit, gas limit, operation bytes etc.

I have the following code to make this estimate.

Tezos transaction class

import { Tezos } from 'taquito/dist/lib/taquito';
import { Estimate } from 'taquito/dist/lib/contract/estimate';
import { XTZSigner } from './xtz-signer';

class XTZTX {
    
    private xtzSigner: XTZSigner;

    constructor() {
        this.xtzSigner = new XTZSigner('tz2B35M8eHC6FhAVsQrtp8EBPri4H73w7W7C'); // my address
        await Tezos.setProvider({ rpc: 'https://api.tez.ie/rpc/mainnet', signer: this.xtzSigner });
    }

    makeEstimate() {
        const receiver = 'tz1i4ezL2FZ1kZ8oqEY8n6wCr2eGRJPC4xin'; // Empty unused address
        const amountToSend = 9900000 // All muTez (9.9 tz) available on my account
        const estimateParams = { to: receiver, amount: 9900000 };
        const estimate = await Tezos.estimate.transfer(estimateParams);
    }
}

Signer class that implements the Taquito Signer interface

import { Signer } from 'taquito/dist/lib/signer/interface';

export class XTZSigner implements Signer {

  private address: string;
  private pubkey: string;

  constructor(address: string) {
    this.address = address;
  }

  publicKeyHash(): Promise<string> {
    return Promise.resolve(this.address);
  }

  publicKey(): Promise<string> {
    const pk = b58cencode(this.pubkey, sppkPrefix);
    return Promise.resolve(pk);
  }

  secretKey(): Promise<string> {
    throw new Error('Secret key cannot be exposed');
  }

  public async sign(
    bytes: string,
    watermark?: Uint8Array
  ): Promise<void> {
    return undefined;
  }
}

So I set the amountToSend variable to my account's full supply (9 900 000 muTez), ran the makeEstimate() function, but then then Tezos.estimate.transfer() returned the following error:

Error: {
      "errors": [
        {
          "kind": "temporary",
          "id": "proto.008-PtEdo2Zk.contract.balance_too_low",
          "contract": "tz2B35M8eHC6FhAVsQrtp8EBPri4H73w7W7C",
          "balance": "9898580",
          "amount": "9900000"
        }
      ],
      "name": "TezosOperationError",
      "id": "proto.008-PtEdo2Zk.contract.balance_too_low",
      "kind": "temporary",
      "message": "(temporary) proto.008-PtEdo2Zk.contract.balance_too_low"
    }

It says my balance is 9898580. But https://tzstats.com/tz2B35M8eHC6FhAVsQrtp8EBPri4H73w7W7C says it is 9900000. I have double-checked this with Taquito's getBalance() function:

Tezos.tz
  .getBalance('tz2B35M8eHC6FhAVsQrtp8EBPri4H73w7W7C')
  .then((balance) => console.log(`${balance.toNumber()}`))
  .catch((error) => println(JSON.stringify(error)));

So I guess Taquito subtracted 1420 from my account's balance. Why 1420, what is this number? Anyway, then I thought I'd decrease the "amount" property to 9898580:

const estimateParams = { to: receiver, amount: 9898580 };

Running the makeEstimate() function again now causes the follow error to be thrown:

    Error: {
      "errors": [
        {
          "kind": "temporary",
          "id": "proto.008-PtEdo2Zk.contract.cannot_pay_storage_fee"
        },
        {
          "kind": "permanent",
          "id": "proto.008-PtEdo2Zk.context.storage_error",
          "missing_key": [
            "contracts",
            "index",
            "06",
            "04",
            "bf",
            "10",
            "9b",
            "5d",
            "00011dd9f2781e3f8c512f871e17d7624e43ad2b4b55",
            "balance"
          ],
          "function": "get"
        }
      ],
      "name": "TezosOperationError",
      "id": "proto.008-PtEdo2Zk.context.storage_error",
      "kind": "permanent",
      "message": "(permanent) proto.008-PtEdo2Zk.context.storage_error"
    }

Okay, so this time I do have enough balance, but I cannot pay the storage fee. So I tried lowering the amount even more to 9000000, and this time it worked. However, I would like to automate this process. Now I can just keep trying to lower the amount until I don't get errors anymore, but I would like to determine this amount automatically so I never get these errors again. Exactly how can I calculate how much I need to subtract so I have enough balance and enough for storage fee? What is the formula for this?

Answer 1

[Edit] As Simon has suggested, the fee has been reduced, and the only restriction is to have 1 mutez left on the account or undelegate the account if the account is used for delegation. Jev suggested a link to the newly provided documentation.

Tezos does not allow for sending the whole address balance, some dust left on the account is required to be able to execute a transaction. Some wallets require a minimum of 0.27XTZ or 0.275XTZ. The official documentation can be found here.

Answer 2

Tezos Taquito has docs on how to drain an account which you can find here: https://tezostaquito.io/docs/drain_account

It covers how to drain implicit and originated accounts.