<p>It's possible you mean 1 of 2 things by "mining reward":</p>

<ol>
<li>Coinbase transaction.</li>
</ol>

<p>Currently this reward is 25 bitcoins per block. If a miner changes this to be higher, it is an invalid block and other nodes will not accept this as a valid block. If the block is not accepted by other nodes, it doesn't go into the blockchain and the miner will not get any bitcoins.</p>

<p>The miner can change the reward <a href="https://github.com/bitcoin/bitcoin/blob/e5f1f5a26399c7d36fa8e2c29ec411eea49b0a4c/src/main.cpp#L1831" rel="nofollow">to be lower</a> than 25 bitcoins currently. This is potentially a way to slow down bitcoins coming into existence, but is otherwise not harmful. There is an economic disincentive for a miner to do this, but it is possible.</p>

<ol start="2">
<li>Transaction fee.</li>
</ol>

<p>This is the difference between the sum of the inputs and sum of the outputs in any given transaction. As the transaction is signed by a private key, any changes to either inputs or outputs will cause the signature embedded in the transaction to be invalid. If this transaction is included in a block, the block itself is invalid and will result in other nodes not accepting this block. Similarly as (1) the block being invalid will cause the block to not get into the blockchain causing the miner to not get any bitcoins.</p>

<p>Basically, the miner is heavily incentivized to act honestly as that's the only way a miner can get bitcoins.</p>

CC BY-SA 3.0
2015-02-06T03:50:18.433Z
`(or lower)` [There's no rule against that, actually.](https://github.com/bitcoin/bitcoin/blob/e5f1f5a26399c7d36fa8e2c29ec411eea49b0a4c/src/main.cpp#L1831)
Nick ODell
CC BY-SA 3.0
2015-02-06T04:00:19.263Z
@NickODell So the miner can do that?
Willipm
CC BY-SA 3.0
2015-02-06T04:01:25.593Z
I stand corrected. I'll change the answer.
Jimmy Song
CC BY-SA 3.0
2015-02-06T05:56:42.630Z
ok, I think I get it
Willipm
CC BY-SA 3.0
2015-02-06T03:41:33.800Z
2015-02-06T04:03:01.660Z
2015-02-06T04:03:01.660Z
Jimmy Song
<p>You know the mining reward is just a number in the code,what if a miner changed it?</p>

<mining-reward><coinbase-transaction><block-validity>
How does the Bitcoin network checks if the miner has changed the mining reward?
Willipm
# How does the Bitcoin network checks if the miner has changed the mining reward?

(Asked by: username_0 on 2015-02-06)

You know the mining reward is just a number in the code,what if a miner changed it?

**Tags:** mining-reward, coinbase-transaction, block-validity


---

## 1 answers

### Answer by username_1 on 2015-02-06. Score: 1 | Accepted answer

It's possible you mean 1 of 2 things by "mining reward":

1. Coinbase transaction.

Currently this reward is 25 bitcoins per block. If a miner changes this to be higher, it is an invalid block and other nodes will not accept this as a valid block. If the block is not accepted by other nodes, it doesn't go into the blockchain and the miner will not get any bitcoins.

The miner can change the reward [to be lower](https://github.com/bitcoin/bitcoin/blob/e5f1f5a26399c7d36fa8e2c29ec411eea49b0a4c/src/main.cpp#L1831) than 25 bitcoins currently. This is potentially a way to slow down bitcoins coming into existence, but is otherwise not harmful. There is an economic disincentive for a miner to do this, but it is possible.

2. Transaction fee.

This is the difference between the sum of the inputs and sum of the outputs in any given transaction. As the transaction is signed by a private key, any changes to either inputs or outputs will cause the signature embedded in the transaction to be invalid. If this transaction is included in a block, the block itself is invalid and will result in other nodes not accepting this block. Similarly as (1) the block being invalid will cause the block to not get into the blockchain causing the miner to not get any bitcoins.

Basically, the miner is heavily incentivized to act honestly as that's the only way a miner can get bitcoins.

> **Comments:**
> **username_2**: `(or lower)` [There's no rule against that, actually.](https://github.com/bitcoin/bitcoin/blob/e5f1f5a26399c7d36fa8e2c29ec411eea49b0a4c/src/main.cpp#L1831)  
> **username_0**: @username_2 So the miner can do that?  
> **username_1**: I stand corrected. I'll change the answer.  
> **username_0**: ok, I think I get it  

---

