Why is Bitcoin transaction not reversible

[VivaMan]

Let's discuss

I've been thinking about asking this phrase until I thought and knew the reasons why..

Carrying transactions using Bitcoin are mainly internationally design to be irreversible once they have been verified on the blockchain note that.

Reasons below:

1. No specific central authority: Bitcoin work's on a decentralized network.

There is no bank, payment processor, or company that  has  the power to reverse  transaction's after it has been confirmed by the receiver.

2. Blockchain immutability:  All transactions are grouped into blocks.
and each block is cryptographically channels to the one before it.
 Changing a past transaction would require rephrase that block and every subsequent block while gaining control of most of the network's computing power.

3. Consensus rules: Once the network reaches consensus that a transactions is validated and includes it in the blockchain, every node updates its copy of the ledger.


4. Protection against massive spending: If transactions could be reversed at will.
someone could spend the same bitcoin twice times  legitimate payments after receiving goods or services.

Irreversibility helps prevent this.

Are there any exceptions?

Before confirmation: If a transaction is still unverify it  may sometimes be replaced with a higher-fee transaction using techniques such as Replace-by-Fee ,  expecially if the original transaction was marked as replaceable to the user.

Custodial services: If you're using an exchange or wallet provider, they may be able to reverse transfers that occur entirely within their own platform before they're settled on the blockchain.

 However, once a transaction is broadcast and confirmed on the Bitcoin network, they cannot reverse it.

Users cooperation: If you mistakenly send bitcoin to the wrong address, the only way to recover it is if the receiver has a good mind to sends it back.

Conclusion

 Bitcoin transactions are not reversible because the system is structure to give a  well permanent, tamper-resistant note  of ownership without depending on a trusted intermediary.

This gives consumers full confidence over their money, but it also means they must be careful to verify addresses and transactions payments before sending bitcoin.

[caroasi]

The biggest reason is that reversals would generally be matters of subjective opinion. Rather than allowing unfair political biases or incorrect judgement of theft, those reversal opportunities are sacrificed for confidence of security against confiscation.

[Aanuoluwatofunmi]

Once a transaction in the Bitcoin network is confirmed, they know that it cannot be reversed, except if the same recipient's address decides to send it back to the sender. This is where we have a different network protocol with Bitcoin, which is quite different from the way the traditional financial system works. A centralized financial authority should not reverse an already confirmed transaction, and this is why the fiat system is not best for security measures, while Bitcoin is bringing these changes into effect through its decentralized network.

[stadus]

There have already been several discussions about this topic in the past.

I think it would be better to search first before creating another thread, because repeated topics like this can easily turn into spam and may eventually get deleted.

Here are some of the older discussions about the same subject:

A Bitcoin transaction is irreversible.
Why is that our bitcoin or cryptocurrency transactions are irreversible.
Bitcoin transactions aren't reversible... I'm confuse

[Ambatman]

Once a transaction in the Bitcoin network is confirmed, they know that it cannot be reversed, except if the same recipient's address decides to send it back to the sender.

Not really
A reorg including ones caused by 51% attack could technically lead to a reversal
Say Alice own 2 BTC and sent 1BTC to Bob in Block A and a reorg occurs
If the transaction isn't included in the new accepted chain
The Bitcoin would be deemed still owned and controlled by Alice
Because according to the new accepted blockchain the transaction never occurred
This is why most wait five or more confirmation
Because it gets more expensive as the confirmation increases for a reorg.

[suzanne5223]

Let's discuss

I've been thinking about asking this phrase until I thought and knew the reasons why..

Carrying transactions using Bitcoin are mainly internationally design to be irreversible once they have been verified on the blockchain note that.

No, it was an intentionally designed feature to make Bitcoin transaction to be immutability and have the potential to completely solve the double-spending problem without relying on trusted third parties.
Nevertheless, most nodes reject classic double spend transactions nowadays, but miners always choose the transaction they add to a block.
It is good to wait for 2-3 confirmations when an UTXO is removed from the UTXO set, because a transaction can be reversed if this has not happened.

[Agbe]

And another reason again there is no one controlling the server to reverse back the wrong transactions and that is why it is always on warning that we should be careful when making bitcoin transactions. Crosscheck the bitcoin receiver's address before clicking the send button. The key word here is the decentralized digital cash transaction system make it so. Since there is no central server to do that.

[legiteum]

ALL serious transactional systems made since the 1960s are "not reversible".

Every transaction-storing system, as Bitcoin is, has a ledger, and that ledger keeps track of all operations on the ledger, not just a balance. Hence every serious financial system ever made does not "reverse" a transaction, it merely adds another transaction to counteract the first one. This is exactly what you would do if you paid for something with Bitcoin and didn't receive it, and complained to the vendor (or sued them, or whatever): you would request an additional transaction in order to get your money back.

The problem Bitcoin has sometimes is that computing newbies, who have never before encountered any other financial system, look at what Bitcoin does and they think it's amazing magic. 

[Charles-Tim]

It is good to know about chain reorg the need of waiting for more confirmations.

Custodial services: If you're using an exchange or wallet provider, they may be able to reverse transfers that occur entirely within their own platform before they're settled on the blockchain.

Nothing even happened on the blockchain because both you and the person are using the same centralized exchanges or custodial wallet.

But if it is a different exchange or wallet, the transaction has to be onchain if sending to another exchange platform or centralized wallet, once the transaction is sent, it is not reversible.

[notocactus]

It is good to know about chain reorg the need of waiting for more confirmations.

With risk of reorg and 51% attacks, there are recommendations on how many Bitcoin confirmations are enough for a transaction and a business deal.

• How many Bitcoin confirmations is enough?
• Bitcoin confirmation risk calculator.
• Calculator on probability of 51% attacks.

If you are patient enough to wait for at least one confirmation then you are no longer vulnerable to race attacks or Finney attacks. Now your only concern is 51% attacks. What's the rule of thumb for an acceptable number of confirmations?

• 1 confirmation: sufficient for small payments less than $1,000.
• 3 confirmations: for payments $1,000 - $10,000. Most exchanges require 3 confirmations for deposits.
• 6 confirmations: good for large payments between $10,000 - $1,000,000. Six is standard for most transactions to be considered secure.
• 10 confirmations: suggested for large payments greater than $1,000,000.

This is an interesting view on this risk and cost of attacks.

Note that someone has to risk three blocks, so your transaction value has to be equal to at least three block rewards (unless the attacker wants to reverse more than that). The majority obviously moves less than 18.75 BTC.

[letteredhub]

And another reason again there is no one controlling the server to reverse back the wrong transactions and that is why it is always on warning that we should be careful when making bitcoin transactions. Crosscheck the bitcoin receiver's address before clicking the send button. The key word here is the decentralized digital cash transaction system make it so. Since there is no central server to do that.

It's not really about how many bitcoins you have and conversions to local currency but about the importance of the irreversibility feature of bitcoin transactions which has helped protected abuse against double spending at any point. This has being made possible through bitcoin network proof of work and  time stamp mechanism which as long as a bitcoin transaction is broadcasted to the miners and validated, it becomes irreversible to be double spent.

Check the: Bitcoin whitepaper

[CryptoHeadlineNews]

The irreversibility of Bitcoin is one of its core principle and feature which Satoshi Nakamoto added to it, in other to make its usage trustworthy among its community of users. And secondly, since it is a decentralized digital currency which has no central control, the feature was added in other to ensure that confirmed payments can not be received back, just like it's been done with the use of bank and credit card whereby a scammer can buy a item online and then later request a for reverse payment and they will be credited back. So in other to avoid such scenario, Satoshi Nakamoto carefully ensured that Bitcoin transaction was designed in such a way that once it's been confirmed on the blockchain. It remains irreversible.

[GeorgeJohn]

And another reason again there is no one controlling the server to reverse back the wrong transactions and that is why it is always on warning that we should be careful when making bitcoin transactions. Crosscheck the bitcoin receiver's address before clicking the send button. The key word here is the decentralized digital cash transaction system make it so. Since there is no central server to do that.

But if bitcoin transactions have not proceed or confirmed and you cancel the transaction. It's obvious that you may likely get your bitcoin, but once it has confirmed, there's no remedy for reversals of the transactions...So based on this fact, it will agree with you for crosschecking a wallet before sending for your transactions to process...

I dont think that people do make such mistakes of copying an address that is not bitcoin address and process it with bitcoin, If check the complains of who have make a mistake vai bitcoin transactions, you note that it's few people that can make such a mistake...actually it's necessary to carefully cross check your address before proceeding to process.

[Synchronice]

Actually, you can reverse Bitcoin transaction before it gets confirmation but in reality, you do not reverse a transaction, you simply replace the transaction but when it comes to confirmation, the thing is that they become progressively harder to reverse but theoretically they are never impossible to reverse. There is a reason companies are waiting for 6 confirmations at least. A transaction with one confirmation can potentially disappear during a blockchain reorganization.
Also, Bitcoin transaction is not verified by the receiver but verified by independent nodes and then included by miners in blocks.

[BlackBoss_]

Actually, you can reverse Bitcoin transaction before it gets confirmation but in reality, you do not reverse a transaction, you simply replace the transaction but when it comes to confirmation, the thing is that they become progressively harder to reverse but theoretically they are never impossible to reverse.

It's double spend on a transaction that has yet been confirmed by Bitcoin miners and relayed by Bitcoin nodes. Reversing transactions is about transactions that already got at least one confirmation.

There is a reason companies are waiting for 6 confirmations at least. A transaction with one confirmation can potentially disappear during a blockchain reorganization.
Also, Bitcoin transaction is not verified by the receiver but verified by independent nodes and then included by miners in blocks.

This explanation in "Mastering Bitcoin" book can give more insights about that and easily to understand. Because of more vulnerability of first blocks like first one, first three or six ones, centralized exchanges usually require 1 to 3 confirmations before either crediting deposit to user account or allowing users to withdraw funds after their deposits.

Chapter 11: The blockchain.

One way to think about the blockchain is like layers in a geological formation, or glacier core sample. The surface layers might change with the seasons, or even be blown away before they have time to settle. But once you go a few inches deep, geological layers become more and more stable. By the time you look a few hundred feet down, you are looking at a snapshot of the past that has remained undisturbed for millions of years.

In the blockchain, the most recent few blocks might be revised if there is a chain reorganization due to a fork.
The top six blocks are like a few inches of topsoil. But once you go more deeply into the blockchain, beyond six blocks, blocks are less and less likely to change.
After 100 blocks back there is so much stability that the coinbase transaction—​the transaction containing the reward in bitcoin for creating a new block—​can be spent. While the protocol always allows a chain to be undone by a longer chain and while the possibility of any block being reversed always exists, the probability of such an event decreases as time passes until it becomes infinitesimal.

[Aanuoluwatofunmi]

Going through what others have suggested and contributed, as well as bitcoin transactions, I could see that there is more to iron out in this discussion.

It is important to do understand the moment a transaction has been included on a block, then it is very difficult to see it reversed, any transaction that was not included on the block will have to go back to the chain for a reorg, you will understand that the importance of number of confirmation of a transaction is also important on this just to attest to the credibility of a transaction by miners.

[MainIbem]

Once a transaction in the Bitcoin network is confirmed, they know that it cannot be reversed, except if the same recipient's address decides to send it back to the sender. This is where we have a different network protocol with Bitcoin, which is quite different from the way the traditional financial system works. A centralized financial authority should not reverse an already confirmed transaction, and this is why the fiat system is not best for security measures, while Bitcoin is bringing these changes into effect through its decentralized network.

That's because unlike banks there's no third-party involved in Bitcoin whereby for instance if you mistakenly transfer money to a wrong address you can report the transaction with evidence or inform your manager so it can be reversed, like it done in the bank Bitcoin was created that way for a purpose, in the sense that you're in control of whatever happens in your wallet that's why everyone has to be very careful when transacting with Bitcoin cause after all the blocks have confirmed a transaction it would be tough reserve their confirmations in the ledger.

[Stalker22]

Let's discuss
~

OK, lets discuss... I think this is probably one of the worse explanations I have ever read.  It reads like a mix of broken ChatGPT slop and someone who bought their first $10 of BTC yesterday trying to lecture the rest of us on day-one basics.

What the hell is "Protection against massive spending"?  How can transaction irreversibility protect us from massive spending?  The term you are probably butchering is double-spending.
"Rephrase that block"?  Did you mean: replace that block?  You know that different words can mean different things, right?
And "each block is cryptographically channels to the one before it" is nonsensical word-salad.  They are linked via cryptographic hashes.
Also, if you dont even know who confirms a transaction, why are you trying to lecture people on immutability?  Just to give you a hint - the recipients are not the ones doing it!

[EL MOHA]

But if bitcoin transactions have not proceed or confirmed and you cancel the transaction. It's obvious that you may likely get your bitcoin, but once it has confirmed, there's no remedy for reversals of the transactions...So based on this fact, it will agree with you for crosschecking a wallet before sending for your transactions to process...

Let’s not actually put the word cancel transaction although that’s what some wallet with that feature named it, but it’s actually a replacement of transaction like the RBF feature this is done by the wallet itself when itself and the new address for replacement is still the sending address, this two is like the RBF though so if the first transaction also gets picked first this will definitely also not happen, although it’s very improbable because the fee for replacement is actually higher than the initial transaction fee and you know miners priority is the fee.

I dont think that people do make such mistakes of copying an address that is not bitcoin address and process it with bitcoin,

Copying wrong bitcoin addresses or addresses not that of bitcoin? It’s never possible as the bitcoin will not be sent, even a wrong address has to be a valid address, that is it has a valid checksum, non bitcoin address doesn’t have this and it’s same for just omitting one character or replacing it too

[Dr.Bitcoin_Strange]

There's no way Bitcoin transactions could have been allowed to be reversed at will. Even on some of the centralized platforms where these kinds of issues have occurred, they were due to either network errors, system glitches, or excessive traffic on the systems being used to process the transactions. It didn't happen at customers will. Those systems are centralized, and customers using the platforms have all their personal details attached to their accounts. So, even when these kinds of errors occur, they can be rectified because the institution would know the person to whom the money was reversed.

Bitcoin is decentralized, and users can be anonymous. So, if this kind of error were to occur with Bitcoin, there would be so much loss of funds, and scammers would get away with it since their identities are not known. It's a good thing that Bitcoin is neither centralized nor affected by such lapses.