# Accurately calculate fees to sweep all coins

We have an instance of bitcoin core running a watch only wallet. This wallet receives a lot of transactions that we need to (once a day) sweep and split into other personal wallets.

The distribution is a full sweep as follows:

1. Each vendor receives 95%, after fee deduction
2. The system collects 5%, after fee deduction

Currently we do it manually like so:

1. Create a new wallet in electrum with addresses that have balance
2. Manually calculate how much each partner is going to receive
3. Manually split the bitcoins for each partner
4. Check how much is the estimated fee for that transaction
5. Recalculate how much each partner is going to receive taking the fee out
6. Manually sign the transaction

Example:

``````Inputs:
Vendor A: 2 BTC in 5 inputs
Vendor B: 1 BTC in 2 inputs
Vendor C: 7 BTC in 20 inputs
Total input transactions: 10 BTC

Assuming fee: 0.0002
We send to each party's personal wallet:
Vendor A: 1.89996200
Vendor B: 0.94998100
Vendor C: 6.64986700
System: 0.49999000

Total sent: 10 BTC
``````

I'm trying to automate the calculation of the distribution with the following script: (please assume `Bitcoin.rpc` is the same as `bitcoin-cli`)

``````balance = Bitcoin.rpc.getbalance '*', 1, true
estimatedFee = ???

vendorABalance = vendorAIncome * (balance - estimatedFee)/balance * 95%
vendorBBalance = vendorBIncome * (balance - estimatedFee)/balance * 95%
vendorCBalance = vendorCIncome * (balance - estimatedFee)/balance * 95%

systemBalance = balance - estimatedFee - vendorABalance - vendorBBalance - vendorCBalance

rtx = Bitcoin.rpc.createrawtransaction [], [
{ 'Vendor A wallet' => vendorABalance },
{ 'Vendor B wallet' => vendorBBalance },
{ 'Vendor C wallet' => vendorCBalance },
{ 'System wallet' => systemBalance },
]
Bitcoin.rpc.fundrawtransaction rtx, { includeWatching: true, conf_target: 6 }

# On a offline machine
rtx = bitcoin-cli signrawtransactionwithkey rtx ['private keys']

# Back on the online machine
Bitcoin.rpc.sendrawtransaction rtx
``````

In theory this script does exactly what I need. If the `estimatedFee` variable gets the correct value

But I can't seem to find the sweet spot that will allow for the sweep of the wallet, I get Insufficient funds or there will be some leftovers.

What can I do?

It seems there is some discrepancy between your `estimatedFee` variable and the feerate being used in the `fundrawtransaction` step.

I think you could try simplifying your code to not use the `estimatedFee` during the `vendorXBalance` calculation, and then when calling `fundrawtransaction`, use the `subtractFeeFromOutputs` option to just have the fee deducted equally from all specified outputs. For example:

``````balance = Bitcoin.rpc.getbalance '*', 1, true

vendorABalance = vendorAIncome * 95%
vendorBBalance = vendorBIncome * 95%
vendorCBalance = vendorCIncome * 95%

systemBalance = balance - vendorABalance - vendorBBalance - vendorCBalance

rtx = Bitcoin.rpc.createrawtransaction [], [
{ 'Vendor A wallet' => vendorABalance },
{ 'Vendor B wallet' => vendorBBalance },
{ 'Vendor C wallet' => vendorCBalance },
{ 'System wallet' => systemBalance },
]
Bitcoin.rpc.fundrawtransaction rtx, { includeWatching: true, conf_target: 6, subtractFeeFromOutputs: [vout_index,...] }

# On a offline machine
rtx = bitcoin-cli signrawtransactionwithkey rtx ['private keys']

# Back on the online machine
Bitcoin.rpc.sendrawtransaction rtx
``````

Here is some relevant text from `bitcoin-cli help fundrawtransaction` (v0.17.0.1):

``````"subtractFeeFromOutputs" (array, optional) A json array of integers.
The fee will be equally deducted from the amount of each specified output.
The outputs are specified by their zero-based index, before any change
• Before I use this solution I have to ask. `equally from all specified outputs`, In the example I gave, everyone will share the same amount to pay the fee, vendorB (1 btc) and vendorC (7 btc) will contribute the same way to the tx fee. Is there no way to have them contribute by "shares" or participation? Commented May 8, 2019 at 10:57