How to unstuck a low-fee transaction with Electrum?

Question

I've sent a transaction with Electrum, but accidentally included too little fee. What can I do to speed up the transaction's confirmation or to replace it?

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^{This is a complementary question to Why is my transaction not getting confirmed and what can I do about it? which answers the question's broader implications and proposes mitigation mostly focused on Bitcoin Core.}

Answer 1

I've just visited #electrum on IRC to get some advice. While restoring from a seed may make your wallet forget a transaction and allow you to resend it with a higher fee, abpa there told me that this sometimes doesn't work because the server will remind the client about the transaction if it's still in the server's mempool.

abpa suggested using child-pays-for-parent to unstuck transactions, i.e. to send a transaction that spends the change output of the previous transaction with a higher fee to pay for both transactions. (Update:) Apparently, the Electrum developers have added GUI-support for CPFP in Electrum 2.8.0 on 2017-03-09.

In general it is recommended to activate replace-by-fee when using Electrum. This allows updating the fee after the transaction was broadcast if it turns out that the first estimate was insufficient. The setting can be found at Tools > Preferences > Fees > Enable Replace-by-Fee.

Answer 2

A method that should work most of the time is the "child pays for parent" method. It is explained here by user maservant: "Child pays for parent means, as the name implies, that spending an unconfirmed transaction will cause miners to consider confirming the parent transaction in order to get the fees from the child transaction included in the same block."

While the post describes the general mechanism very well, I couldn't find a detailed description on how to apply it in Electrum. Hence, I wrote up a detailed description myself. You can find it here.

In short:

• First, find out if an output of the unconfirmed transaction went to yourself by checking the details in the "History" tab. If so, write down the hash
• Then, go to the "Coins" tab, select the corresponding hash, right-click and select "Spend from Address". This will take you to the "Spend" tab
• Here, enter one of your own receiving addresses. Thus, you will create a new transaction, containing as an input part of the unconfirmed transaction. When miners confirm this new transaction, the former, unconfirmed one has to be confirmed as well. This is what solves your issue.
• Add a fee high enough to make both transactions worthwhile for miners. To do so, check https://bitcoinfees.21.co/ and apply their recommendation to the combined size of both your transactions
• If your "change" address does not contain enough coins for this, you can transfer the total amount of your respective wallet instead. This will also include your unconfirmed output (if there was an output to yourself) as an input to the new transaction
• Broadcast the transaction. When it is confirmed, the former transaction should be confirmed as well.

Answer 3

You might want to ask ViaBTC.com to accelerate your transaction. If your transaction includes a minimum of 0.0001BTC/KB fee, you can submit your txid to the Transaction Accelerator so ViaBTC prioritize your transaction. The 100 submissions limit resets every full hour.

Answer 4

If you are using Electrum, there is no equivalent to -zapwallettxes. The closest thing you can do is to restore your wallet from a seed. This will wipe your client of any unconfirmed transactions.

Then, you can resend the transaction with a higher fee.