What is block subsidy?

The newly created coins paid to whoever mines a block, separate from the transaction fees also collected in that block.

Bitcoin's subsidy began at 50 BTC and halves every 210,000 blocks, about every four years, which caps total supply just under 21 million coins (source: Bitcoin developer documentation). Fees are the other half of the reward, and as the subsidy shrinks, fees become the larger share of what miners earn.

Do not confuse the subsidy with the total block reward. Pages that quote one for the other overstate or understate miner income, and the gap between them widens with every halving.

How it works

The subsidy is the only way new coins are created on Bitcoin. It is claimed in the coinbase transaction, the first transaction in every block, which has no inputs because the coins did not exist before.

Bitcoin Core computes it by starting at 50 coins and applying one halving per subsidy halving interval of 210,000 blocks, forcing the value to zero once 64 halvings have occurred (source: Bitcoin Core, GetBlockSubsidy in validation.cpp). Summing that geometric series is where the 21 million figure comes from; there is no separate cap rule in the code.

A miner may claim less than the allowed subsidy, and a few have done so by mistake, permanently reducing the eventual supply.

Coinbase outputs carry a maturity rule: they cannot be spent for at least 100 blocks (source: Bitcoin developer documentation). That protects anyone who receives a payment traced to a recent reward from a chain reorganization undoing it.

Proof-of-stake chains have an equivalent concept, issuance paid to validators, but it is usually a continuous rate tied to the amount staked rather than a fixed amount per block.

Example

Illustrative: at a 3.125 BTC subsidy and about 144 blocks a day, new issuance is roughly 450 BTC per day. If average fees run 0.09 BTC per block, fee income is about 13 BTC a day, so fees are about 2.8% of total miner revenue. After the next halving to 1.5625 BTC, the same fee level would be about 5.5%. Figures are illustrative and fee income varies enormously by day.

Why it matters when you buy

The subsidy is the rate at which new supply arrives, which is one factor in supply and demand and is fully published years ahead. Its decline also shifts the cost of chain security onto transaction fees, which over time affects what it costs you to move coins. Compare withdrawal charges across venues at the fee comparison and see the Bitcoin asset page.

Related terms

• block reward — subsidy plus fees combined
• bitcoin halving — the event that cuts it
• coinbase transaction — how it is paid out
• mining — the activity it funds
• emission schedule — the general term for issuance over time
• hard cap — the supply limit the schedule produces

Questions

Is the subsidy the same as the block reward?

No. The subsidy is the newly created coins only. The block reward is the subsidy plus the transaction fees in that block, and the fee share grows as the subsidy falls.

Can the subsidy schedule be changed?

Only by consensus across the network, which would require node operators, miners, and users to adopt incompatible rules. It has never been changed and there is no mechanism for one party to do it.

Why can miners not spend rewards immediately?

Because a reorganization could remove the block that created them. The 100-block maturity rule means the reward is deeply buried before it can circulate.