LThis guide explains how to use the Coin Control feature when sending bitcoin. It allows you to manually choose which of your coins (UTXOs) you want to spend, giving you greater control over your privacy and transaction details.

How to select coins for a transaction

Once the feature is enabled, you can follow these steps to build your transaction.

Prepare the transaction

1. From a Bitcoin account, click the Send button.

2. On the transaction screen, enter the recipient's address and the amount you wish to send. 
3. Click the Coin control button to open the coin selection panel.

Select your coins (UTXOs)

4. In the Coin Control window, you can now see your UTXOs and the following details: 
   1. Label (unique name if one was set)
   2. BTC amount, 
   3. Value in fiat
   4. Below that the date when the UTXO was created
   5. The address where it’s located
   6. And the outpoint as a unique identifier.
5. Click the checkbox next to one or more UTXOs on the left to select them as inputs for your transaction.

Pay attention to the labels next to each coin:

• A blue "Change" label indicates a UTXO that came from the change of a previous transaction.
• A red "Address re-used" label is a privacy warning, indicating the address has been used more than once.

 

Choose your sending method

You have two ways to send the selected coins.

To send a specific amount

1. Ensure you have entered an amount in the Amount field.
2. Select UTXOs whose combined value is greater than the send amount plus the network fee.
3. The BitBoxApp will use your selected coins to fund the transaction. The remaining amount will be returned to a new change address in your wallet.

To send the full value of selected coins

1. Select the UTXOs you wish to consolidate or send.
2. Click the Send selected coins checkbox. This replaces the Amount field.
3. The transaction will send the entire balance of the selected UTXOs, minus the network fee.

Finalize the transaction

1. Review the final transaction details in the BitBoxApp summary.
2. Verify the recipient address, amount, and fee on your BitBox02's secure screen.
3. If all details are correct, confirm the transaction on your BitBox02.

Frequently Asked Questions

What happens if I don't select enough coins to cover the amount and the network fee?

The BitBoxApp will not let you proceed. The Send button will be disabled, and a message will indicate that the selected funds are insufficient. You will need to select additional coins to cover the total transaction cost.

What happens if I click on 'Send all' without using coin control?

When Coin Control is not active, the checkbox on the send screen is labeled Send all. Ticking this box will create a transaction to send the entire balance of that account to the recipient you entered. The BitBoxApp will automatically select all the necessary coins (UTXOs) to do this.

What does the "Address re-used" tag mean?

This is a privacy warning. It means the address associated with that coin has been used for more than one transaction (either sending or receiving). For best privacy, it is recommended to use a new address for every transaction. This tag helps you identify and avoid spending from reused addresses if you choose to.

Do I have to select a change address?

No. The BitBoxApp automatically handles the change for you. If the total value of the coins you select is greater than the amount you are sending (plus the network fee), the remaining amount will be sent back to a new change address in your wallet.