The last bitcoin is expected to be mined around the year 2140, when the mining reward drops below one satoshi (the smallest unit of bitcoin, equal to 0.00000001 BTC). At that point, no new bitcoin will ever enter circulation, and miners will rely entirely on transaction fees to sustain the network. The shift won’t happen overnight, though. It’s a gradual process that’s already underway with each halving event.
Why 2140 Is the Target Year
Bitcoin’s creator, Satoshi Nakamoto, built a hard cap of 21 million coins into the protocol. New bitcoin enters circulation through block rewards, which are payments miners receive for validating transactions and adding them to the blockchain. Every 210,000 blocks (roughly every four years), those rewards are cut in half in an event called “the halving.”
The first miners earned 50 BTC per block. After the most recent halvings, that reward has shrunk dramatically, and it will keep shrinking. After about 30 halvings from Bitcoin’s launch, the reward becomes smaller than one satoshi, making it effectively zero. That’s projected to happen around 2140. At that point, approximately 21 million bitcoin will exist, and no more can ever be created.
In practical terms, the vast majority of bitcoin has already been mined. Over 19.7 million of the 21 million coins are already in circulation. The remaining supply will trickle out in increasingly tiny amounts over the next century-plus.
Miners Switch to Transaction Fees Only
Today, miners earn money from two sources: the block reward (newly created bitcoin) and transaction fees (small amounts paid by users to have their transactions processed). The block reward is currently the larger share of mining income, but its importance shrinks with every halving. Transaction fees will need to pick up the slack.
Once the block reward hits zero, transaction fees become the sole incentive for miners to keep running their hardware and securing the network. This isn’t a sudden cliff. Each halving gradually shifts the balance, giving the ecosystem decades to adapt. By the time 2140 arrives, the block reward will have been negligible for many years already.
The open question is whether transaction fees alone will be large enough to keep a sufficient number of miners operating. If fees are too low, some miners will shut down, reducing the computing power that protects the network. If fees are robust, the transition could be seamless.
The Security Budget Problem
The most serious concern about a post-reward Bitcoin is what’s often called the “security budget” problem. The total amount paid to miners, whether through block rewards or fees, is what incentivizes them to behave honestly. If that total drops too low, the network becomes more vulnerable to attacks.
Researchers at MIT Media Lab have studied one specific risk: undercutting attacks. In this scenario, a miner intentionally forks the blockchain to steal transaction fees from an already-mined block. This type of attack becomes more attractive when block subsidies disappear, because the transaction fees sitting in recent blocks represent a larger share of potential profit. The result could be increased instability if miners start competing to re-mine each other’s blocks rather than building on top of them.
This doesn’t mean the network will collapse. It means the incentive structure changes, and Bitcoin’s developer community will likely need to address these dynamics through protocol adjustments, fee market design, or other innovations well before 2140.
What Drives Transaction Fees Higher
For the fee-only model to work, Bitcoin needs consistent demand for block space. Several factors could push fees higher over time. Growing adoption means more people and institutions competing to get their transactions confirmed. Limited block size means space in each block remains scarce. And high-value transactions, like large settlements between institutions, naturally command higher fees because users are willing to pay more for timely confirmation.
There’s a counterforce worth understanding, though. Layer 2 solutions like the Lightning Network allow users to conduct transactions off the main blockchain, settling only periodically on-chain. Research published in IEEE Xplore found that Lightning Network adoption could reduce miners’ fee revenue from smaller transactions, which are a significant income source. Users sending small payments can bypass the main chain entirely, meaning fewer individual fee-paying transactions for miners to collect.
The same research found a tradeoff, however. While Lightning may reduce fee income measured in bitcoin, it expands the overall user base and transaction volume by making Bitcoin more practical for everyday payments. A larger, more active network could increase the value of on-chain settlement fees even if fewer small transactions occur on the base layer. The long-term effect may be net positive, but the transition creates real uncertainty for mining economics.
Bitcoin’s Supply Stays Fixed Forever
Once the last bitcoin is mined, the total supply is permanently locked. No central authority can issue more. This is fundamentally different from fiat currencies, where central banks can expand the money supply at will. It’s also different from gold, where new deposits can still be discovered and extracted.
In practice, the effective supply is even smaller than 21 million. Researchers estimate that millions of bitcoin are permanently lost, locked in wallets whose private keys have been forgotten, destroyed, or buried with their owners. Those coins can never be recovered or spent. As more coins are lost over time, the circulating supply slowly shrinks, making remaining bitcoin scarcer.
This fixed supply is central to Bitcoin’s appeal as a store of value. Supporters argue that predictable, zero-inflation monetary policy makes bitcoin a reliable long-term asset. Critics counter that deflation (a rising value per coin) could discourage spending and create hoarding dynamics that limit Bitcoin’s usefulness as a currency.
What Changes for Everyday Users
If you hold or use bitcoin, the end of mining rewards won’t change your experience in any dramatic, immediate way. You’ll still send and receive bitcoin the same way. Your coins won’t expire or lose functionality. The 21 million cap is already baked into the protocol and has been priced into the market for years.
What could change is the cost of transacting. If transaction fees need to rise significantly to keep miners profitable, on-chain transactions could become expensive enough that small, everyday payments move almost entirely to Layer 2 networks. The base blockchain could evolve into a settlement layer for large or important transactions, while routine payments happen off-chain.
The transition to a fee-only model is one of the most debated topics in the Bitcoin community, and it will play out over generations. The halving cycle keeps cutting rewards in half, giving developers, miners, and users decades to observe how fee markets develop and adjust the system accordingly. By the time the last satoshi is mined, the economics of mining will have been shaped by over a century of real-world data.