Bitcoin Forum

I just sent a 0.1BTC transaction. Now it shows that I also paid 0.9BTC to another address (http://imgur.com/pUdOTPG). I used the Bitcoin QT client to do the transaction. There it told me that I spent 0.00001130BTC transaction fee. The Bitcoin QT Client is not fully synchronized yet (about 1 year behind). Could that be a problem?

The funds are moved to another address but in the same wallet, can you see the balance of 0.89998870 in your wallet?
https://www.blocktrail.com/BTC/tx/02573c6348c72f37d3d9187c645779d296c6e9d1b3753816f11c50c7dc282dc1

Have you had 1 BTC in your wallet? Or was there a 1 BTC transaction? I looks for me that you are using different addresses in one wallet and the 0.9 BTC transaction was just a reorganization between those addresse because you have not had 0.1 BTC in the senders address. In this case, everything is good.

What you experienced is called change.

-> https://en.bitcoin.it/wiki/Change

An example:

Lets assume your wallet has got a balance of 1 BTC. You are using two addresses in your wallet.
Balance of address 1: 0.1 BTC
Balance of address 2: 0.9 BTC

Now you send 0.12 BTC from address 1 to a third address (what is not part of your wallet). Because you have only 0.1 BTC, there happens a automatic reorganization. 0.9 BTC are transferred from address 2 to address 1 and then 0.12 BTC are sent to address 3. Afterwards, address 1 has a balance of 0.88 BTC and address 2 has got nothing anymore. The overall balance of your wallet is 0.88 BTC. It has just been reorganized between the addresses in your wallet. All this happens in one transaction.

Ok, thanks for the information.
So for the change a new address I being created and automatically added to my wallet?

In Bitcoin QT when I show all my "receiving addresses", I can only see my one address. Not the other one where the 0.9BTC went to. I guess this is because Bitcoin QT is not fully synchronized yet?

I am fairly certain that "change addresses" do not appear in that list - but you can see them if you switch on Coin Control and click on the Inputs button in the Send dialog.

In general there is no need to worry about them - just pay attention to your Balance and check your Transactions list (to work out whether or not it is confirmed).

But *do* remember to back up your wallet after every X transactions (for your own piece of mind I'd do that after every few txs but technically X is the number of keys/addresses that have been generated in advance which by default is 100).

In a sense yes. Bitcoin core 100 address pregenerated for you. The pool of pregenerated address will refill when needed. This is why you need regular backups no matter how many or few addresses you have in "receiving addresses".


No, change address - as CIYAM said - do not appear in that list you need to enable coin control.

To do so:

-> Settings -> Options -> Wallet -> check "Enable coin control feature" -> confirm with ok

Now to see the address, Im pretty sure core needs to sync first, but you can see it here:

-> Send -> Inputs -> check "Tree mode" -> search for your known address and click the small triangle to the left. It will open up and show the other address labeled as "(change)".

With coin control enabled I was able to see the change addresses (and their balance, even if sync is not finished; but I do not see the confirmations yet of cours).

Regarding backups:
I have some backups on external usb drives of my wallet. So I have to replace those over and over again?

You would be best advised to never overwrite an existing backup but instead make new backups regularly (just in case something goes wrong with your latest backup there should always be at least one previous one that might help recover funds).

To make it easier to remember what is what you could include the date in the name of the backup.

Ok. Thanks.

afaik those are hidden address, i usually do "listaddressgroupings" on the debug window---> console to see them

they are a pain in the ass for the backup because after 100 of those are created they are not stored anymore in the mem pool , and you risk to lose your coins, without another new backup

may be your type mistake to input 0.9,instead if 0.1

ok it's just a change address