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Replace-by-fee (RBF) Bitcoin

Replace-by-fee (RBF) is a feature that allows users to replace one version of an unconfirmed transaction with a different version of the transaction that pays a higher transaction fee. This can be done multiple times while the transaction is unconfirmed.

The benefits of RBF are that it allows you to gradually increase the fee until the transaction is accepted into a block. If the need to confirm a transaction becomes more urgent than initially thought, RBF also allows the sender to easily accelerate the transaction and have it added to the next block.

RBF was proposed in BIP125 and the initial implementation was released in Bitcoin Core 0.12.0. 

  • Replace-by-fee in Trezor Suite
  • Enabling and disabling RBF
  • Bump a transaction fee
  • Finalizing a transaction
  • RBF by output reduction
  • Replace-by-fee with Trezor in Electrum


Replace-by-fee in Trezor Suite

RBF is now fully implemented in Trezor Suite as of version 21.2.2 and also has on-device support for Trezor Model T with firmware 2.3.5 and up, as well as Trezor Model One with firmware 1.9.4 and up. 

There are two ways to use RBF in Trezor Suite: to bump (increase) the fee or to finalize the transaction.

Enabling and disabling RBF

RBF is enabled by default in Trezor Suite. To turn it off, click the RBF toggle before sending a transaction:

If RBF is disabled, it will not be possible to increase the fee and low-fee transactions may go unconfirmed or fail


Bump a transaction fee

Choosing to bump a fee will open a dialog where a new custom fee can be set. This fee must be higher than the previous fee as it adds the difference to the total set in the previous transaction.

Once a new fee is selected in Suite, the transaction must be confirmed once again on your Trezor device, which will display the original transaction that is being replaced and the total fee to be paid.

This process can be repeated as many times needed. A total of all fee bumps will be paid.


Finalizing a transaction

Some merchants (in particular those who would normally accept unconfirmed transactions) do not trust RBF-flagged transactions until a certain number of confirmations. In such cases, RBF can be turned off before paying them, or an existing transaction can be finalized. 

Clicking on Finalize transaction in the pending transaction pop-up dialog will send a replacement transaction that is identical but has the RBF flag turned off.

RBF by output reduction

When sending the maximum amount of bitcoin stored on a single account, there will be no leftover balance to increase the fee from. RBF by output reduction takes the additional fee from the amount being transferred, instead of the account balance.

Using RBF output reduction can be done in the same way as bumping the fee, as long as RBF was enabled when the transaction was sent.
  • To speed up confirmation times when sending the full balance of an account, click Bump fee on the pending transaction.
  • A new window will open where a new fee can be set.
  • Trezor Suite will show a message that there are no funds left for the fee, and that the amount sent must be reduced.
  • Set a new fee and confirm the new settings. The additional fee will then be reallocated from the transaction output.


Replace-by-fee with Trezor in Electrum

It is possible to use Replace-by-fee with Trezor device in Electrum. The original transaction can be replaced only if it was made using Electrum with the "Replace by fee" option on (Tools - Preferences - Replace by fee).

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