Coinbase maturity: separate issued from spendable bitcoin
Here “coinbase” means a block’s reward transaction, not the exchange with the same name. Its outputs have a consensus maturity restriction. Bitcoin issued into a reward output can therefore exist onchain while still being unavailable to spend in a transaction included at the selected height.
The Bitcoin block-chain guide describes the 100-block maturity condition for coinbase outputs. Apply the rule to the actual output and proposed spending-block height. The worksheet is about consensus eligibility, not a miner’s legal ownership, profitability, or intention to sell.
Use a height test, not a calendar guess
Record the creation height h for each unspent reward output. A spend included at height H must satisfy H − h ≥ 100, in addition to every other applicable validity condition. Define H explicitly. A state snapshot at tip T and a question about inclusion in the next block use related but different reference points.
For a next-block test, set H = T + 1. Under this convention, a coinbase output created at h = 1,000 becomes eligible for inclusion at H = 1,100. Do not label it spendable in block 1,099 merely because a dashboard rounds elapsed time to a day. The rule counts blocks, not hours.
Keep principal quantities separate from labels such as circulating or liquid. A provider may classify miner rewards differently in its published supply measure. Consensus maturity is a narrower, reproducible property. Losing access to a private key is a different limitation and cannot be inferred from whether the height threshold is satisfied.
Hypothetical rolling inventory
Assume a fictional miner has unspent reward outputs of 3.2 BTC created at height 1,000 and 3.3 BTC created at height 1,050. These amounts include hypothetical subsidy and fee receipts; they are not a statement about the current block reward.
| Proposed inclusion height | First output | Second output | Eligible amount |
|---|---|---|---|
| 1,099 | Immature | Immature | 0 BTC |
| 1,100 | Mature | Immature | 3.2 BTC |
| 1,150 | Mature | Mature | 6.5 BTC |
The full 6.5 BTC exists in the fictional output inventory before both outputs mature. At height 1,100, only the first 3.2 BTC passes this specific condition. Other spending conditions still need checking. “Mature” should not be translated into “sold,” “free of restrictions,” or “available on an exchange.”
If the first output is spent later, remove it from the unspent inventory rather than leaving it in the mature balance forever. The new non-coinbase outputs have their own scripts and histories; they do not inherit a fresh coinbase-maturity period merely because their inputs originated in mining rewards.
Reconcile the inventory each block
Build three buckets: immature unspent rewards, mature unspent rewards, and outputs already spent. Add newly observed reward outputs, move eligible outputs between the first two buckets as H advances, and subtract spent outputs. Distinguish a transfer to another wallet from newly issued value.
Preserve block hashes with heights. If a reward block is removed from the selected chain, its output cannot simply remain in the inventory under the old height. A rerun must remove or relink affected records. Confirmation-count conventions in wallet software may use presentation rules that differ from the proposed-inclusion test, so check boundary cases explicitly.
For a miner-liquidity note, add independently verified custody, contractual and wallet-control limitations after this consensus reconciliation. Do not subtract the same immature amount twice if a provider’s “available balance” already excludes it. State whether the final number is a raw reward inventory, a maturity-adjusted amount, or an operationally accessible balance.
The resulting schedule explains when a specific restriction expires. It cannot predict a miner’s cash needs, bitcoin sales, or price pressure. Reopen it when the chain selection changes or new output spending evidence arrives.
A reward’s subsidy and included transaction fees share the same output-level maturity treatment when paid into that coinbase output. Do not release the fee component earlier merely because it originated from existing coins. Conversely, a miner’s separately received ordinary transfer is not a coinbase output merely because the recipient also operates mining equipment.
FAQ
Does coinbase maturity refer to a withdrawal rule at an exchange?
No. It refers here to Bitcoin’s block-reward outputs and their consensus spending condition.
Is 100 blocks an exact number of hours?
No. Block intervals vary. Use the output height and proposed inclusion height rather than converting the threshold into a guaranteed calendar time.