can you reverse or cancel a bitcoin transaction?

[Naster]

It has been said sometimes that a Bitcoin transaction can be cancelled or reversed using for example double-spend.
Is it still possible? If Yes, how? If No, Why?
Especially when you sell services and goods and accept Bitcoin payment, you are worried about this.
So it should be a good idea to discuss this topic.

[mocacinno]

It has been said sometimes that a Bitcoin transaction can be cancelled or reversed using for example double-spend.
Is it still possible? If Yes, how? If No, Why?
Especially when you sell services and goods and accept Bitcoin payment, you are worried about this.
So it should be a good idea to discuss this topic.

You can't cancel or revert a transaction.

However, there are a couple "tricks" you can pull while a transaction is UNCONFIRMED.

For example, you can create a (very) low-fee transaction, and broadcast it to as little nodes as humanly possible. Then, create a new transaction, using the same unspent outputs as input but funding a completely different address as the first transaction. You can create this secondary transaction with a much higher fee and broadcast it to as many nodes as possible.
If you do this, there is a decent chance a miner will put the second transaction into the block he's currently working on instead of the first one. And once one of those transactions ends up in a valid, broadcasted block that's been added to the blockchain, the other transaction is automatically "voided". It's using unspent outputs that are no longer in the UTXO set, so the unconfirmed tx becomes invalid.

If you're setting up a service, it's always a good idear to wait for at least 1 confirmation before sending goods or services. For expensive products, you might even chose to wait 3+ confirmations ( 6+ for the really paranoid shop owners). Once a transaction has a couple of confirmations, there is no way of cancelling or reversing it.

[stompix]

It has been said sometimes that a Bitcoin transaction can be cancelled or reversed using for example double-spend.
Is it still possible? If Yes, how? If No, Why?

An already confirmed transaction that has been included in a block can't be cancelled.

So it should be a good idea to discuss this topic.

It is a better idea to search before starting a new thread:
https://bitcointalk.org/index.php?topic=1922415.0
https://bitcointalk.org/index.php?topic=1901899.0
https://bitcointalk.org/index.php?topic=1238034.0
https://bitcointalk.org/index.php?topic=151430.0
https://bitcointalk.org/index.php?topic=1742325.0
https://bitcointalk.org/index.php?topic=1177722.0
https://bitcointalk.org/index.php?topic=1516140.0
https://bitcointalk.org/index.php?topic=1012583.0

[Naster]

It has been said sometimes that a Bitcoin transaction can be cancelled or reversed using for example double-spend.
Is it still possible? If Yes, how? If No, Why?

An already confirmed transaction that has been included in a block can't be cancelled.

So it should be a good idea to discuss this topic.

It is a better idea to search before starting a new thread:
https://bitcointalk.org/index.php?topic=1922415.0
https://bitcointalk.org/index.php?topic=1901899.0
https://bitcointalk.org/index.php?topic=1238034.0
https://bitcointalk.org/index.php?topic=151430.0
https://bitcointalk.org/index.php?topic=1742325.0
https://bitcointalk.org/index.php?topic=1177722.0
https://bitcointalk.org/index.php?topic=1516140.0
https://bitcointalk.org/index.php?topic=1012583.0

Of course, a search is always helpful. I agree with you!
However, these threads are outdated, and in some of them, it has not been clearly answered.
The technology is moving forward and we need to know what is the actual stand.
I've read about double spending and found this for example

It is when a person broadcast two seperate transactions which spends the same outputs. Since the majority of the network runs Bitcoin Core, the reference client, they would first receive the first transaction and store it in their mempool. The other transaction will then be rejected. It is fairly hard to attempt to doublespend the transaction on the blockchain but it can be accomplished. If you have a transaction which has low fees, wait till most of the peers drops your transaction in the mempool then you can broadcast it again. Blockchain.info used to have a page to allow people to test it out but it's removed already. There are also some open sourced programs that allows you to double spend but I can't guarantee it is safe since you have to give your private key.

Blockchain.info seems to be rebroadcasting your transaction whenever it gets dropped out of mempool. Get the private key and delete it out from your blockchain.info, store it somewhere safe then wait for a week. After that, verify that it has dropped out of the mempool and import it to a desktop client to send the BTC. That's what I have done before anyway.

But is there someone who has been able (recently) to cancel a broadcasted transaction?

or is it definetely that there is NO WAY to cancel a transaction?

Thus it makes sense to discuss it again.

[mocacinno]

--snip--

But is there someone who has been able (recently) to cancel a broadcasted transaction?

or is it definetely that there is NO WAY to cancel a transaction?

Thus it makes sense to discuss it again.

I have a habit of cheaping out on fees when i move funds between my own wallets. Nowadays, i always opt-in RBF, which makes it very easy to create a double spending transaction with a higher fee and broadcast it, but about a year ago, i did have to create new transactions doublespending the unspent outputs used and input of my own transactions several times. It was during the spam attack and the astronomical fees, and before opt-in RBF was adopted in my wallet, so many of my low-fee between-my-own-wallet transactions got "stuck". doublespending was the fasted way of fixing these problems.

It can be done, but like i said: if you wait for 1+ confirmations, the transaction can no longer be "cancelled" this way.

[evilgreed]

--snip--

But is there someone who has been able (recently) to cancel a broadcasted transaction?

or is it definetely that there is NO WAY to cancel a transaction?

Thus it makes sense to discuss it again.

I have a habit of cheaping out on fees when i move funds between my own wallets. Nowadays, i always opt-in RBF, which makes it very easy to create a double spending transaction with a higher fee and broadcast it, but about a year ago, i did have to create new transactions doublespending the unspent outputs used and input of my own transactions several times. It was during the spam attack and the astronomical fees, and before opt-in RBF was adopted in my wallet, so many of my low-fee between-my-own-wallet transactions got "stuck". doublespending was the fasted way of fixing these problems.

It can be done, but like i said: if you wait for 1+ confirmations, the transaction can no longer be "cancelled" this way.

           I actually like your idea about double spending, now back to the topic, i guess there is no way it is reversable, that is why you need to check it multiple times before making a transaction. There are also notifications that tells each user that it cannot be reversed, so you have to be aware, once it is confirmed, there is no turning back, and no regrets when it is done.

[dangdangdang]

If the transaction is confirmed already then you cannot undone it. But otherwise I read some tricks that will make some adjustments while the transaction isn't confirmed yet. I found it in the first page of this this thread but I didn't verify since you need to do it accordingly.

[TheGodson]

You don't need to worry about double spending. If you make a transaction using bitcoin there isn't anyway to cancel the request. Once it is made it is made. The only way to stop a transaction by double spending is if the transaction isn't confirmed. In the real world people wait until transactions are confirmed in order for it to mean anything.

[wahyu5]

bitcoin transaction that we have done will not be canceled, this is the system that I think is very good from bitcoin after we do bitcoin transaction then we just wait for the results of the transaction

[Coyster]

After one block confirmation it becomes impossible to reverse, that is why before to carry out a transaction it's best you be 100% sure of the address and other necessities, many have unknowingly sent bitcoins to the wrong address or to a scammer, manual checking is also necessary sometimes

[mocacinno]

you can reverse bitcoin transactions made by your own wallet with https://dcryptex.com

I visited this site and quickly scanned the explanation they gave on how they cancel transactions, and all i can say is: that's not how this works... As soon as a transaction is confirmed, it's allmost impossible to cancel the transaction unless you own enough asic's to do a 51% attack... Any site claiming otherwise are a potential scam

[evanescence]

It is trivial to do before the first confirmation. You'll require hundreds of millions in mining equipment after the first one. This is not how bitcoin used to work a few years ago so a lot of merchants get scammed.

[rollingstorm45]

If the transaction is confirmed already then you cannot undone it. But otherwise I read some tricks that will make some adjustments while the transaction isn't confirmed yet. I found it in the first page of this this thread but I didn't verify since you need to do it accordingly.

the transaction has taken place then it cannot be canceled. like we pulled the trigger once pulled then it can't be canceled. be careful before making a transaction and don't rush into doing a transaction before we are sure of everything we do.

[Astvile]

You cant reverse or cancel a bitcoin transacton as far as i know,but there are tricks to not totally cancel bitcoin transaction but to remain unconfirmed and later on get back on the senders wallet i dont know how they do that but thats what i only know.

[taufik0911]

just as you will transfer money from bank A to bank B where after the confirmation notification appears and you confirm that your transaction is correct then you cannot cancel the transaction because your transaction is being processed and cannot be canceled by the system

[stompix]

you can reverse bitcoin transactions made by your own wallet with <no thanks>

I visited this site and quickly scanned the explanation they gave on how they cancel transactions, and all i can say is: that's not how this works... As soon as a transaction is confirmed, it's allmost impossible to cancel the transaction unless you own enough asic's to do a 51% attack... Any site claiming otherwise are a potential scam

This one is not a potential scam, it's a 100% genuine scam



Not only is their claim hilarious, but their script is also bugged, that address I posted and the tx are not 521 days old, they are 9 years old. Furthermore, they ask you for "Private key or your seed pharse" , yeah, pharse .

Fortunately, it seems that the payment address is always the same, no matter what you try and till now it has 0 transactions.

[Ezenwanyi1]

Personally, I do not believe that bitcoin transaction can be cancelled after it's sent.
My assumption is that ...miners start the mining of bitcoin immediately it's the sent button is clicked.
There's no way of knowing which miner so as to signify to the person to cancel the transaction or reverse it.
It's just too complicated.

[killat]

Bitcoin transactions cannot be cancelled. The process is irreversible and this is how the network has been built.

Personally,  I find that as a good thing, as I wouldn't want to see that a transaction I had in my wallet during the night has been cancelled in the morning.

[KennyR]

The transaction through bitcoin is a single way system. Once transferred will not get back an access to the funds anymore until the receiver manages to send back to the sender. With this before making a bitcoin transaction it is a must to be much careful. There is a possibility to cancel a transaction if it hasn't got connected to the block.

[nauane]

Personally, I do not believe that bitcoin transaction can be cancelled after it's sent.
My assumption is that ...miners start the mining of bitcoin immediately it's the sent button is clicked.
There's no way of knowing which miner so as to signify to the person to cancel the transaction or reverse it.
It's just too complicated.

I was thinking of what is the one drawback which bitcoin has ?  The only drawback is that if you sent the amount to wrong address or wrong amount to the right address even, the process cannot be reversed and therefore one should be extra careful when sending bitcoins to any address.