<p>Each transaction has a unique identifier which is the <code>txid</code>. It is the hash of the transaction and each transaction's hash is unique.</p>

CC BY-SA 4.0
2018-11-01T04:42:04.530Z
No, one txid can cause multiple entries in the `list*` RPCs. You need to also include "vout" to have a unique key.
Pieter Wuille
CC BY-SA 4.0
2021-01-18T19:00:09.197Z
@PieterWuille what is considered a valid "receive" transaction from listsinceblock that I would about to credit? If say same txid occurs in 2 transactions but with different vout, should both transactions be credited? What if 2 transactions have same txid and vout? Thank you
daniel
CC BY-SA 4.0
2021-01-18T19:32:19.900Z
Yes you should credit both. The same txid/vout combination can't appear multiple times.
Pieter Wuille
CC BY-SA 4.0
2018-05-14T23:39:10.330Z
2018-05-14T23:39:10.330Z
Ava Chow
<p>I am trying to understand if there a unique identifier for transactions. I didn't find anything about that mentioned in <a href="http://chainquery.com/bitcoin-api/help/listsinceblock" rel="nofollow noreferrer">listsinceblock</a>'s help.</p>

<pre><code>{
  "involvesWatchonly": true,
  "account": "",
  "address": "mvd6qFeVkqH6MNAS2Y2cLifbdaX5XUkbZJ",
  "category": "receive",
  "amount": 10,
  "label": "",
  "confirmations": 69,
  "blockhash": "62967ce950fc03b14179e58f42e426b63cbfbf63c2b9e59acb6a719a09c23b94",
  "blockindex": 58,
  "blocktime": 1524872287278,
  "txid": "aac9b2d7bb7b3476a83a5ac0c2fe21625bcd961ed43a5c5fd3eacf6536dc81d5",
  "vout": 7,
  "walletconflicts": [],
  "time": 1524872276635,
  "timereceived": 1524872276635,
  "bip125-replaceable": "no"
},
</code></pre>

CC BY-SA 4.0
2018-05-14T23:35:20.480Z
What do you mean by "unique key of transactions over time"? `listsinceblock` does not tell you how many transactions occurred over a given amount of time, it only tells you what transactions and you can then calculate it yourself.
Ava Chow
CC BY-SA 4.0
2018-05-14T23:36:25.967Z
@AndrewChow if I do 2 calls or listsinceblock I want not to count the same transaction twice.
0x90
CC BY-SA 4.0
2018-05-14T23:37:07.700Z
RPC calls are stateless, they do not remember the last time you made that call and do not do anything related to "time since last RPC call". The only way to avoid counting the same transaction twice is to just use the hash of the block that was found after your last call to `listsinceblock`
Ava Chow
CC BY-SA 4.0
2018-05-14T23:38:13.083Z
@AndrewChow that's why I need to take care of it. Then I want a unique identifier
0x90
<listtransactions>
What's a unique identifier in listsinceblock output?
0x90
# What's a unique identifier in listsinceblock output?

(Asked by: username_0 on 2018-05-14)

I am trying to understand if there a unique identifier for transactions. I didn't find anything about that mentioned in listsinceblock's help.
{
  "involvesWatchonly": true,
  "account": "",
  "address": "mvd6qFeVkqH6MNAS2Y2cLifbdaX5XUkbZJ",
  "category": "receive",
  "amount": 10,
  "label": "",
  "confirmations": 69,
  "blockhash": "62967ce950fc03b14179e58f42e426b63cbfbf63c2b9e59acb6a719a09c23b94",
  "blockindex": 58,
  "blocktime": 1524872287278,
  "txid": "aac9b2d7bb7b3476a83a5ac0c2fe21625bcd961ed43a5c5fd3eacf6536dc81d5",
  "vout": 7,
  "walletconflicts": [],
  "time": 1524872276635,
  "timereceived": 1524872276635,
  "bip125-replaceable": "no"
},

**Tags:** listtransactions

> **Comments:**
> **username_1**: What do you mean by "unique key of transactions over time"? `listsinceblock` does not tell you how many transactions occurred over a given amount of time, it only tells you what transactions and you can then calculate it yourself.  
> **username_0**: @AndrewChow if I do 2 calls or listsinceblock I want not to count the same transaction twice.  
> **username_1**: RPC calls are stateless, they do not remember the last time you made that call and do not do anything related to "time since last RPC call". The only way to avoid counting the same transaction twice is to just use the hash of the block that was found after your last call to `listsinceblock`  
> **username_0**: @AndrewChow that's why I need to take care of it. Then I want a unique identifier  

---

## 1 answers

### Answer by username_1 on 2018-05-14. Score: 0

Each transaction has a unique identifier which is the `txid`. It is the hash of the transaction and each transaction's hash is unique.

> **Comments:**
> **username_2**: No, one txid can cause multiple entries in the `list*` RPCs. You need to also include "vout" to have a unique key.  
> **username_3**: @PieterWuille what is considered a valid "receive" transaction from listsinceblock that I would about to credit? If say same txid occurs in 2 transactions but with different vout, should both transactions be credited? What if 2 transactions have same txid and vout? Thank you  
> **username_2**: Yes you should credit both. The same txid/vout combination can't appear multiple times.  

---

