<p>Yes, simply put, Coinbase and some other wallet/merchant services have internal bookkeeping. </p>

<p>So you've deposited 2 BTC. Soon thereafter coinbase will move funds around:</p>

<ul>
<li>to cover other deposits/withdrawals</li>
<li>to exchange</li>
<li>to put in a hot/cold wallet</li>
</ul>

<p>Once you've deposited your Bitcoin, just like a bank, you're effectively given an IOU (unless for services like Blockchain.info you own the private keys) and your withdrawal will draw upon either a single or multiple inputs to reimburse you. </p>

<p>The main reason this is done is twofold:</p>

<ul>
<li>to cut down on Txn fees</li>
<li>because the bitcoin protocol always sends the full input amount (the remainder is sent as change)</li>
</ul>

<p>By coupling change outputs as credits this allows for internal bookkeeping. </p>

<p>(It's worth noting that the txn fee wasn't paid by you directly. It's just a standard multi input txn)</p>

CC BY-SA 4.0
2020-06-22T12:50:59.670Z
Which other wallet services?
Jonathan Ray
CC BY-SA 3.0
2014-12-12T05:28:35.477Z
2014-12-12T05:28:35.477Z
Wizard Of Ozzie
<p>In <a href="https://blockchain.info/tx/c33292e05db5296afec060a5e00dc25d7083674bad0e4462a0335cfa46849490" rel="nofollow noreferrer">this transaction</a>, I transferred 2 BTC from my Coinbase.com wallet to an external address.</p>

<p><img src="https://i.sstatic.net/d4wp4.jpg" alt="Transaction Outputs"></p>

<p>Why are there 3 outputs in the transaction?</p>

<p>I understand the output of 2 BTC, and the 0.0001 BTC transaction fee.  One of the outputs is likely a change address.  But I don't know what the 3rd output is for.</p>

<p>Is/does Coinbase.com</p>

<ul>
<li>combine unrelated user transactions into a single blockchain transaction?</li>
<li>tracking user's funds or transactions off the blockchain (effectively commingling funds)?</li>
<li>extracting its own fee from the transaction?</li>
</ul>

<transactions><coinbase.com>
Is Coinbase.com combining / commingling transactions or funds?
Chuck Batson
# Is Coinbase.com combining / commingling transactions or funds?

(Asked by: username_0 on 2014-12-12)

In [this transaction](https://blockchain.info/tx/c33292e05db5296afec060a5e00dc25d7083674bad0e4462a0335cfa46849490), I transferred 2 BTC from my Coinbase.com wallet to an external address.

![Transaction Outputs](https://i.sstatic.net/d4wp4.jpg)

Why are there 3 outputs in the transaction?

I understand the output of 2 BTC, and the 0.0001 BTC transaction fee. One of the outputs is likely a change address. But I don't know what the 3rd output is for.

Is/does Coinbase.com

* combine unrelated user transactions into a single blockchain transaction?
* tracking user's funds or transactions off the blockchain (effectively commingling funds)?
* extracting its own fee from the transaction?

**Tags:** transactions, coinbase.com


---

## 1 answers

### Answer by username_1 on 2014-12-12. Score: 2 | Accepted answer

Yes, simply put, Coinbase and some other wallet/merchant services have internal bookkeeping.

So you've deposited 2 BTC. Soon thereafter coinbase will move funds around:

* to cover other deposits/withdrawals
* to exchange
* to put in a hot/cold wallet

Once you've deposited your Bitcoin, just like a bank, you're effectively given an IOU (unless for services like Blockchain.info you own the private keys) and your withdrawal will draw upon either a single or multiple inputs to reimburse you.

The main reason this is done is twofold:

* to cut down on Txn fees
* because the bitcoin protocol always sends the full input amount (the remainder is sent as change)

By coupling change outputs as credits this allows for internal bookkeeping.

(It's worth noting that the txn fee wasn't paid by you directly. It's just a standard multi input txn)

> **Comments:**
> **username_2**: Which other wallet services?  

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