The Coinbase Transaction: How Miners Get Paid

The coinbase transaction is the first transaction in every Bitcoin block: it has one placeholder input, creates the new coins, collects the fees, and its outputs say who gets paid. This explainer covers its input and coinbase field, the subsidy (3.125 BTC since the April 2024 halving) plus fees, why it normally has more than one output, and the 100-block wait.

Category: Mining and the Network · Published 2026-10-28

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The first transaction in every block

Open any Bitcoin block and look at the very top of its list of transactions. The first one is always special. It is called the coinbase transaction, and it is the transaction that pays the block's reward to the miner, or the mining pool, that found the block.¹

Every other transaction in a block moves coins that already exist from one owner to another. The coinbase transaction is different: it is where brand-new bitcoin is created and where the block's reward is collected. There is exactly one coinbase transaction per block, no more and no less, and it always sits in first place.²

Why it has no normal inputs

A normal Bitcoin transaction has inputs and outputs. The inputs point back to coins you received earlier and prove you are allowed to spend them; the outputs say where those coins go. You can only send what you already own: a normal transaction whose outputs are worth more than its inputs is rejected.¹

The coinbase transaction breaks that rule on purpose. It creates coins that did not exist a moment ago, so there is no earlier payment for it to point back to. Instead of a real input, it carries exactly one placeholder input that references nothing: a previous transaction ID of all zeros and an output number of 0xffffffff, which every node recognizes as meaning this is a coinbase.³

That placeholder input has a useful side effect. Its script, often called the coinbase field, can hold up to 100 bytes, and apart from the block height it can be any data the miner likes.³ Miners put things there such as:

The block height, which the rules have required since March 2013 (BIP34) so that each coinbase transaction is unique.⁴
An extra nonce: extra room to vary the block while searching for a valid hash.³
Short tags or messages, such as a name. The coinbase field of block 973,413, for example, holds its height and a short tag naming the solo pool that mined it.⁵

Subsidy plus fees: the two halves of the reward

A miner's reward is made of two separate parts, and the coinbase transaction combines them into its outputs.¹

The block subsidy: freshly created bitcoin, 3.125 BTC per block since the April 2024 halving.⁶ The subsidy is cut in half every 210,000 blocks, roughly every four years, in an event called the halving, and it steps down toward zero.²
The transaction fees: the leftover value that the senders of all the other transactions in the block chose to pay, meaning the difference between each transaction's inputs and outputs. The miner collects the total.¹

So the most a miner can claim is the subsidy plus every fee in the block, and a coinbase that pays out more makes the whole block invalid.² As the subsidy keeps halving over the coming decades, fees are meant to carry a growing share of the reward, and in the end all of it. The subsidy is also the only way new bitcoin is ever created, which is what ties Bitcoin's limit of just under 21 million coins directly to this one transaction.⁶ What happens as the subsidy approaches zero looks further ahead.

More than one output

The coinbase transaction has exactly one input, but it can have many outputs, and it normally has more than one. A block that contains SegWit transactions must commit to their witness data in an extra output of the coinbase, one whose script begins with OP_RETURN, so it can never be spent.⁷ A pool can also split the reward across several addresses. Block 973,413, mined through a solo pool on 27 October 2026, shows both: its coinbase pays 3.07689054 BTC to one address and 0.06279368 BTC to another, and carries a zero-value witness commitment as a third output.⁵

It has nothing to do with the company Coinbase

The shared name causes confusion, so let's be blunt: the coinbase transaction and the exchange company named Coinbase are completely unrelated.

In Bitcoin, coinbase is a technical term. Bitcoin's developer documentation uses it for this reward transaction and for its special input, the coinbase field described above.³ The exchange is a separate company that shares the word and nothing else. When Bitcoin's own software or a block explorer says coinbase, it means the miner's reward transaction, never the exchange.

Why it matters for solo mining

Here is where the coinbase transaction becomes very concrete. Whoever builds a candidate block builds its coinbase transaction, which means they choose the payout addresses in its outputs. A solo miner running its own node writes its own address; in pooled mining, the pool's server builds the coinbase, usually paying the pool, and sends your miner only the pieces it needs to hash.⁸ Whoever's address is written there is the one who gets paid if that block is found.

This payout is not an afterthought bolted on later. The coinbase transaction is folded into the block's merkle root, the single fingerprint of every transaction that sits inside the block header being hashed.¹ In other words, the reward destination is locked into the very thing the miner is racing to solve: change it afterward and the proof of work no longer matches.

For a solo miner with its own node, that address is simply their own wallet: find a block, and the coinbase pays the subsidy and fees straight to them, with no custodian holding the funds. A solo pool that writes each miner's own address into the coinbase works the same way, less any fee it takes as its own output.

The 100-block wait before it can be spent

There is one honest caveat worth knowing. Coins from a coinbase transaction cannot be spent right away: the rules require them to mature for 100 blocks before they can move.¹ Since a block arrives roughly every ten minutes on average, that wait usually works out to something like sixteen or seventeen hours.

The reason is safety. Occasionally two miners find a block at almost the same moment and the network briefly disagrees about which one counts; one of those blocks ends up stale and is dropped. The maturity delay makes sure a freshly minted reward cannot be spent until its block is buried deep enough that it is very unlikely to be replaced. If a block does end up stale, its coinbase pays nothing: the reward only exists on the chain the network keeps.¹

FAQ

Is the coinbase transaction the same as the Coinbase exchange?

No. The coinbase transaction is Bitcoin's built-in reward transaction, and coinbase is the word Bitcoin's own software and documentation use for it. The exchange named Coinbase is a separate company that shares the word and nothing else.

Where do the coins in the block subsidy come from?

They are newly created by the coinbase transaction itself. Unlike a normal payment, the subsidy has no previous owner. It is the one and only way new bitcoin comes into existence, and the halving schedule keeps the total supply just under 21 million coins.

How much does a miner earn per block?

At most the block subsidy plus all the transaction fees in that block. The subsidy has been 3.125 BTC since the April 2024 halving and halves every 210,000 blocks. The fee portion varies from block to block depending on how much the senders chose to pay, and any pool fee comes out of the total.

Why does a miner have to wait before spending the reward?

Coinbase rewards must mature for 100 blocks, about 16 to 17 hours on average, before they can be spent. This guards against spending a reward from a block that later turns out to be stale, which can happen when two blocks are found at nearly the same time.

Who decides which address the reward is paid to?

Whoever builds the block. A solo miner with its own node writes its own address; in a pool, the pool's server builds the coinbase. The payout addresses sit in the coinbase outputs, and the coinbase is committed into the block header through the merkle root, so the payout cannot be changed afterward without redoing the work.

Key takeaways

Every block's first transaction is its coinbase transaction, and a block has exactly one.
It has one placeholder input that points at nothing, plus a free-form coinbase field holding the block height, an extra nonce and often a short tag.
Its outputs can claim at most the block subsidy (3.125 BTC since the April 2024 halving) plus the block's transaction fees.
It normally has more than one output, such as the SegWit witness commitment or a pool's share of the reward.
Coinbase coins cannot be spent until 100 blocks have passed, and the name has nothing to do with the exchange called Coinbase.

Sources

Some specific claims in this article are scheduled for further source review; citations may be expanded (see our editorial policy).