transactions – I sent Bitcoin to an address but the recipient hasn’t yet received it

The Blockchain is the only truth

At the time I wrote this, that transaction has 204 confirmations. That means it was absolutely definitely received.

If the address is correct and the recipient says they didn’t “receive” it, they are wrong. Either their wallet isn’t properly synchronised or they are mistaken (or lying to you)

Note that Bitcoin doesn’t actually send money from wallet to wallet, it isn’t a process that takes time between sending and receiving. At no point in time is money really out of one wallet and “on its way” to another wallet.

The only thing transmitted is a new block being transmitted to every node (wallets etc) in the Bitcoin world roughly every ten minutes. So long as you have the latest block, you know exactly which address has the money.

What follows is to clarify my point about the process taking no time. You should skip it unless you are interested in this detail or find it controversial.

Duration of transaction

Let’s consider in a little more detail what happens when you make a typical Bitcoin payment. Note that Bitcoin is pretty complex, so I’ll be simplifying. There are exotic forms of payment I won’t cover (RBF, n of m, …). My knowledge is limited but I think I can shed a little more light on this subject.

When you make a payment in your wallet, what happens is that your wallet constructs a kind of proposal for a transaction. This proposal is sent out into some nearby nodes in the Bitcoin network.

After sending that proposal, your wallet will mark the input amount as reserved for that transaction and won’t let you try to spend it again. Your wallet will however know that this amount is still under your control and still as much “in your wallet” as it ever was and not yet in anyone else’s wallet.

After a short time your proposed transaction will have been passed from node to node, being checked at each, and will reach some miners. Eventually a miner will incorporate your proposed transaction in a block and successfully mine that block.

Before this instant in time, the miner considers the money to be yours. After this instant in time, the miner considers the money to be the recipient’s. There is no time when the miner considers the money to be in transit.

The miner transmits the new block to nearby nodes. As each node finishes checking the new block, that is the instant that particular node stops believing the money belongs to you and starts believing the money belongs to the recipient.

The new block is passed from node to node until it reaches your wallet, At the instant in time it finishes checking that block your wallet ceases believing the money is yours and starts believing (provisionally†) that the money now belongs to the recipient.

There is no time in between. No time when your wallet believes the money is in neither wallet, in transit between wallets, sent but not yet received. None of those are really possible.

There is time during which the proposed transaction is circulating, but during that time all nodes consider the money to be yours. All nodes will accept other proposals from you for another transaction involving that money. This is because until one of those proposals gets included in a mined block, the money is still yours, still unspent.

The circulation of a proposed transaction takes time. Mining takes time. The Bitcoin network is large, so there are times when some nodes have the latest block and some don’t. We say the network has not reached consensus – although each node has no doubt about whether the money is yours or the recipient’s.

The change in ownership of money is instant (at each node separately) and money is never really “in between wallets”.

†Blockchain Forking

Since there are many independent miners (and mining pools), it can be that there are two or more blocks mined at about the same time competing to be accepted as the generally accepted next block. This means that sometimes a recently accepted block is discarded in favour of another block which has a greater number of subsequent blocks mined “on top of” it. This is why nodes generally wait for at least five blocks to be mined on top of the block containing your transaction (six blocks in total) before they accept the change of ownership of money as being fully confirmed.

So there is a period of time between the first block being mined and the sixth block being mined when a node might regard the change of ownership of the money as not sufficiently confirmed. This doesn’t mean a node is unsure about who has the money. It doesn’t mean the money is in transit. It doesn’t mean the Bitcoin network can issue a second transaction to take money back out of the recipient’s wallet. It just means that there is a tiny possibility the Bitcoin network might collectively decide your proposed transaction never got mined in the first place, that it never happened, nothing to see, move along. In most cases where this happens, the forgotten proposed transaction automatically gets included in some subsequent block and everything is OK and everyone forgets there was ever a hiccup.

This doesn’t happen to every transaction, this is rare, it isn’t really a case of money being “in transit” or “not in either wallet” or “not yet received”.

Terminology and philosophical aspects

Proposed Transactions

Above I talk about proposed transactions and proposals. Those words are not generally used in the Bitcoin community. Mostly people talk about transactions, unconfirmed transactions and confirmed transactions. I wanted to use a different word to clearly distinguish a transaction which is circulating which has not yet been mined.

What is in your wallet?

The reason I put “in your wallet” inside scare-quotes the first time I mentioned it is that Bitcoin wallets don’t really contain money. They contain a secret number, called a private-key, that can be used to prove you control some money (own some money). Anyone else who knows that secret number can take money “out of your wallet” from afar without any access to your wallet! Money isn’t stored inside Bitcoin wallets but we go along with the charade because it is a useful shorthand that makes it easier to talk about Bitcoin. It is a useful way to explain Bitcoin to beginners even though it is misleading and unsafe.

This is weird!

Other people will feel my description of the way Bitcoin works places too much emphasis on the underlying dry technical (scary?) nature of transactions and that it is better to describe the process as if paper banknotes were taken out of your leather wallet, moved through an intermediary organisation and then placed into someone elses leather wallet. I agree this view has some utility but I worry it gives the impression that there is time in which banknotes are not in the senders wallet and not in the recipient’s wallet but in the hands of some intermediary who can be asked to return them or intervene to change the outcome. Consider a literal reading of the original title of the question at the top of this page.