<p>When a miner find a valid hash he had to write the new block according to  <a href="https://en.bitcoin.it/wiki/Protocol_rules" rel="nofollow noreferrer">the bitcoin protocol rules</a>, if he try to cheat, like writing that instead of the 12.5 bitcoin that issued to the bitcoin miners (him) it is 50 bitcoin, the network will refuse and ignore this block till he write it properly or someone else write it with the good hash and the right rules.</p>

<p>So in your case the protocol said that there will be no more bitcoin issued after <a href="https://bitcoin.stackexchange.com/questions/10486/when-will-the-last-bitcoin-be-mined/">the year 2140</a> if the protocol does not change, a winning miner have to be careful to follow the rules when he issue his block or he can loose his coins since another will see the winning hash but not the proper block, so he will write the block himself with the winning hash and the proper rules and take the coins for him.</p>

CC BY-SA 4.0
2019-10-25T19:53:27.330Z
*"the protocol of the bitcoin network which is agreed by more than 51% of the miners"* this is false, a majority of miners cannot arbitrarily decide on the network's rules. It is the network's nodes which decide this. If a majority of miners change the rules, then the network's nodes will simply ignore the new blocks they create.
chytrik
CC BY-SA 4.0
2019-10-25T20:47:29.277Z
In order to change the bitcoin protocol you have to do a hard fork, am i right?
Zheer
CC BY-SA 4.0
2019-10-25T21:05:17.693Z
@Zheer not necessarily, what you have to do is submit a BIP and then depending on the modification it can be a soft or a hard fork, see this article https://medium.com/@galea/bitcoin-development-who-can-change-the-core-protocol-478b8ac5fe43
Saxtheowl
CC BY-SA 4.0
2019-10-25T22:29:54.480Z
@Zheer: The miners could collectively enforce a soft fork, i.e. a tightening of rules to reduce the valid set of actions to a subset. The miners cannot loosen rules unilaterally as blocks would get rejected by the nodes that still enforce the rules.
See here for a more comprehensive explanation: https://bitcoin.stackexchange.com/a/30821/5406
Murch
CC BY-SA 4.0
2019-10-25T18:37:31.527Z
2019-10-25T20:14:16.393Z
2019-10-25T20:14:16.393Z
Saxtheowl
<p>Bitcoin block reward gets cut in half, mathematically limiting the reward. This happens every 4 years, roughly speaking. The block reward hits 0 when the amount mined is 21 million. The reward keeps declining until this happens.</p>

CC BY-SA 4.0
2019-10-27T18:59:41.390Z
2019-10-27T18:59:41.390Z
Number File
<p>The Bitcoin protocol allows block authors to create a limited amount of new bitcoins in the outputs of the <a href="/questions/tagged/coinbase-transaction" class="post-tag" title="show questions tagged &#39;coinbase-transaction&#39;" rel="tag">coinbase-transaction</a> (which also collects the transactions fees) in each block. The amount of the so called <em>block subsidy</em> is limited by the consensus rules.<sup>1</sup> <strong>Creating more than the allowed amount makes a block invalid to other Bitcoin nodes.</strong> </p>

<p>Each full node unilaterally enforces the consensus rules. This means that while a miner would be able to create a block that breaks the consensus rules, every other full node in the network would recognize it as invalid, drop the block, and ban the peer that sent it to them.</p>

<p>A change in the consensus rules that allows blocks that were previously considered invalid is called a <a href="https://bitcoin.stackexchange.com/q/30817/5406">hardfork</a>. Hard forks require social consensus of the complete ecosystem or will cause a split of the network as each node operator determines for themselves which software to run. Even if a majority of the hashrate and a majority of the network's nodes hardforked to a new version of the Bitcoin protocol that allowed blocks with a higher block reward, the remaining nodes enforcing the original consensus rules would consider it invalid and continue to follow their own rules. Therefore, an intolerant minority may be able to veto a hardfork, especially if this minority has a significant share of the economic weight. If the economic majority prefers the original rules, miners following the hardforked chain may find it difficult to sell their mining reward. This is essentially what happened in the case of the SegWit2x hardfork attempt.</p>

<p>In the case that both protocol versions have some economic support, a persistent fork may be calved in the form of an airdropped altcoin. This is essentially what happened in the cases of Bitcoin Cash spinning out from Bitcoin, and Bitcoin Cash calving Bitcoin SV.</p>

<hr>

<p><sup>1</sup><sub>
The block subsidy started at 50 bitcoin per block and halves every 210,000 blocks. We're currently in the third era where miners are allowed to create 12.5 bitcoin per block. Having recently passed block 600,000, more than 18,000,000 bitcoins have been found already, and the next halving to 6.25 bitcoins per block is coming up at block 630,000 in spring 2020.</sub></p>

CC BY-SA 4.0
2019-10-25T20:46:36.173Z
How does the bitcoin protocol detect if more than the allowed limit of bitcoin is created?
Zheer
CC BY-SA 4.0
2019-10-25T22:27:42.857Z
The protocol doesn't. Every other full node does, though. Every single full node individually rejecting the invalid block then causes the block to be rejected by the network collectively.
Murch
CC BY-SA 4.0
2019-10-26T09:51:14.837Z
So basically if you do 51% attack, you will be able to create more bitcoin, am i right?
Zheer
CC BY-SA 4.0
2019-10-26T12:34:21.007Z
@Zheer: No.  A 51% attack gives you the ability to create a longer blockchain (in terms of work) than everyone else put together, which will be accepted by conforming nodes as the true blockchain **if it consists of valid blocks**.  But if your blocks create more bitcoins than the protocol allows, then they are invalid and conforming nodes will reject your chain, no matter how long it is.
Nate Eldredge
CC BY-SA 4.0
2019-10-26T13:39:35.833Z
@Nate Eldredge if you control most of the nodes say(90%) how can the confirming nodes prevent you from creating more bitcoins than the protocol allows?
Zheer
CC BY-SA 4.0
2019-10-26T15:24:15.103Z
Well, there is certainly nothing stopping you from mining your own chain following different rules, and awarding yourself as many coins as you like.  But anyone who is still running an ordinary node or client will not consider those coins to be "bitcoins".  If you try to use those coins to pay someone running an ordinary client, their software will not tell them they have been paid, and they won't give you any goods or services in exchange for those coins.
Nate Eldredge
CC BY-SA 4.0
2019-10-26T15:25:27.293Z
@Zheer: It's analogous to me firing up my laser printer and printing millions of "dollar bills" with my face instead of George Washington's.  Sure, I can make as many as I want, but everyone can see that they are not the same as the "real" bills, and they won't accept them as payment or give me goods or services in exchange.
Nate Eldredge
CC BY-SA 4.0
2019-10-26T15:27:53.597Z
@Zheer: It is of course possible that people would *decide* to adopt a client with a higher limit, just as they could decide to start using my money in place of the US dollars issued by the Federal Reserve.  They could even decide to start using the name "Bitcoin" for the new protocol, just as they could decide my money is now the "real" US dollar.  But it would require a conscious decision.
Nate Eldredge
CC BY-SA 4.0
2019-10-26T15:29:05.297Z
@Zheer: And by the way, none of this has anything to do with how much mining power is controlled.  You can mine your own chain, with your own rules, whether you have 1% of the mining power or 51% or 99.9%.  But other nodes still get to decide what protocol they want to follow; you can't force them to change.
Nate Eldredge
CC BY-SA 4.0
2019-10-25T18:48:56.940Z
2019-10-27T18:32:09.337Z
2019-10-27T18:32:09.337Z
Murch
<p>What prevents miners from mining more bitcoin after 21million btc was mined?</p>

CC BY-SA 4.0
2019-10-25T18:40:54.250Z
related: https://bitcoin.stackexchange.com/q/161/5406, https://bitcoin.stackexchange.com/q/13374/5406, https://bitcoin.stackexchange.com/q/2756/5406,
Murch
<mining-reward><reward-schedule><money-supply>
What prevents miners from mining more bitcoin after 21million btc?
Zheer
# What prevents miners from mining more bitcoin after 21million btc?

(Asked by: username_0 on 2019-10-25)

What prevents miners from mining more bitcoin after 21million btc was mined?

**Tags:** mining-reward, reward-schedule, money-supply

> **Comments:**
> **username_1**: related: https://bitcoin.stackexchange.com/q/161/5406, https://bitcoin.stackexchange.com/q/13374/5406, https://bitcoin.stackexchange.com/q/2756/5406,  

---

## 3 answers

### Answer by username_1 on 2019-10-25. Score: 4 | Accepted answer

The Bitcoin protocol allows block authors to create a limited amount of new bitcoins in the outputs of the [coinbase-transaction](/questions/tagged/coinbase-transaction "show questions tagged 'coinbase-transaction'") (which also collects the transactions fees) in each block. The amount of the so called *block subsidy* is limited by the consensus rules.1 **Creating more than the allowed amount makes a block invalid to other Bitcoin nodes.**

Each full node unilaterally enforces the consensus rules. This means that while a miner would be able to create a block that breaks the consensus rules, every other full node in the network would recognize it as invalid, drop the block, and ban the peer that sent it to them.

A change in the consensus rules that allows blocks that were previously considered invalid is called a [hardfork](https://bitcoin.stackexchange.com/q/30817/5406). Hard forks require social consensus of the complete ecosystem or will cause a split of the network as each node operator determines for themselves which software to run. Even if a majority of the hashrate and a majority of the network's nodes hardforked to a new version of the Bitcoin protocol that allowed blocks with a higher block reward, the remaining nodes enforcing the original consensus rules would consider it invalid and continue to follow their own rules. Therefore, an intolerant minority may be able to veto a hardfork, especially if this minority has a significant share of the economic weight. If the economic majority prefers the original rules, miners following the hardforked chain may find it difficult to sell their mining reward. This is essentially what happened in the case of the SegWit2x hardfork attempt.

In the case that both protocol versions have some economic support, a persistent fork may be calved in the form of an airdropped altcoin. This is essentially what happened in the cases of Bitcoin Cash spinning out from Bitcoin, and Bitcoin Cash calving Bitcoin SV.

---

1The block subsidy started at 50 bitcoin per block and halves every 210,000 blocks. We're currently in the third era where miners are allowed to create 12.5 bitcoin per block. Having recently passed block 600,000, more than 18,000,000 bitcoins have been found already, and the next halving to 6.25 bitcoins per block is coming up at block 630,000 in spring 2020.

> **Comments:**
> **username_0**: How does the bitcoin protocol detect if more than the allowed limit of bitcoin is created?  
> **username_1**: The protocol doesn't. Every other full node does, though. Every single full node individually rejecting the invalid block then causes the block to be rejected by the network collectively.  
> **username_0**: So basically if you do 51% attack, you will be able to create more bitcoin, am i right?  
> **username_5**: @username_0: No.  A 51% attack gives you the ability to create a longer blockchain (in terms of work) than everyone else put together, which will be accepted by conforming nodes as the true blockchain **if it consists of valid blocks**.  But if your blocks create more bitcoins than the protocol allows, then they are invalid and conforming nodes will reject your chain, no matter how long it is.  
> **username_0**: @username_5 if you control most of the nodes say(90%) how can the confirming nodes prevent you from creating more bitcoins than the protocol allows?  
> **username_5**: Well, there is certainly nothing stopping you from mining your own chain following different rules, and awarding yourself as many coins as you like.  But anyone who is still running an ordinary node or client will not consider those coins to be "bitcoins".  If you try to use those coins to pay someone running an ordinary client, their software will not tell them they have been paid, and they won't give you any goods or services in exchange for those coins.  
> **username_5**: @username_0: It's analogous to me firing up my laser printer and printing millions of "dollar bills" with my face instead of George Washington's.  Sure, I can make as many as I want, but everyone can see that they are not the same as the "real" bills, and they won't accept them as payment or give me goods or services in exchange.  
> **username_5**: @username_0: It is of course possible that people would *decide* to adopt a client with a higher limit, just as they could decide to start using my money in place of the US dollars issued by the Federal Reserve.  They could even decide to start using the name "Bitcoin" for the new protocol, just as they could decide my money is now the "real" US dollar.  But it would require a conscious decision.  
> **username_5**: @username_0: And by the way, none of this has anything to do with how much mining power is controlled.  You can mine your own chain, with your own rules, whether you have 1% of the mining power or 51% or 99.9%.  But other nodes still get to decide what protocol they want to follow; you can't force them to change.  

---

### Answer by username_2 on 2019-10-25. Score: 1

When a miner find a valid hash he had to write the new block according to [the bitcoin protocol rules](https://en.bitcoin.it/wiki/Protocol_rules), if he try to cheat, like writing that instead of the 12.5 bitcoin that issued to the bitcoin miners (him) it is 50 bitcoin, the network will refuse and ignore this block till he write it properly or someone else write it with the good hash and the right rules.

So in your case the protocol said that there will be no more bitcoin issued after [the year 2140](https://bitcoin.stackexchange.com/questions/10486/when-will-the-last-bitcoin-be-mined/) if the protocol does not change, a winning miner have to be careful to follow the rules when he issue his block or he can loose his coins since another will see the winning hash but not the proper block, so he will write the block himself with the winning hash and the proper rules and take the coins for him.

> **Comments:**
> **username_3**: *"the protocol of the bitcoin network which is agreed by more than 51% of the miners"* this is false, a majority of miners cannot arbitrarily decide on the network's rules. It is the network's nodes which decide this. If a majority of miners change the rules, then the network's nodes will simply ignore the new blocks they create.  
> **username_0**: In order to change the bitcoin protocol you have to do a hard fork, am i right?  
> **username_2**: @username_0 not necessarily, what you have to do is submit a BIP and then depending on the modification it can be a soft or a hard fork, see this article https://medium.com/@galea/bitcoin-development-who-can-change-the-core-protocol-478b8ac5fe43  
> **username_1**: @username_0: The miners could collectively enforce a soft fork, i.e. a tightening of rules to reduce the valid set of actions to a subset. The miners cannot loosen rules unilaterally as blocks would get rejected by the nodes that still enforce the rules. See here for a more comprehensive explanation: https://bitcoin.stackexchange.com/a/30821/5406  

---

### Answer by username_4 on 2019-10-27. Score: -1

Bitcoin block reward gets cut in half, mathematically limiting the reward. This happens every 4 years, roughly speaking. The block reward hits 0 when the amount mined is 21 million. The reward keeps declining until this happens.


---

