Bitcoin crossed the 20 million circulating supply threshold early Tuesday morning, leaving fewer than one million coins remaining to be mined.
Despite many news outlets announcing this milestone on Monday, a historical deficit of roughly 518 permanently destroyed coins delayed the actual event until Tuesday morning. The 518 unspendable coins stem from early network anomalies. The pseudonymous creator Satoshi Nakamoto mined an unspendable 50 coins in the genesis block at the network launch. Furthermore, duplicate coinbase transactions overwrote another 100 coins during the earliest days of the cryptocurrency.
Miners also permanently lost hundreds of coins by accidentally claiming less than their full block subsidy over the years. Consequently, these unspendable coins are permanently removed from the total issued supply.
Tyler Whittle discussed these early mining anomalies and protocol vulnerabilities in a February 2026 Blockspace podcast. Whittle outlined the history of the duplicate coinbases and the genesis block that originally created the 518 coin gap.
Bitcoin’s to-be-mined supply is programmatically reduced roughly every four years in what is known as the halving. The halving mechanism dictates that the block reward will continue to reduce by 50% every 210,000 blocks. This issuance schedule ensures the remaining supply enters circulation at a consistently decreasing rate. The last halving – which will reduce the Bitcoin block subsidy to zero – is expected to occur around the year 2140.
Header image by Kanchanara via Unsplash.
Charlies Spears contributed reporting.
