Anonymous Bitcoin payments: how to break the link between sender and recipient
Every bitcoin transaction reveals much more than just the transfer amount. Along with the payment, change inevitably enters the blockchain, exposing the lower bound of the sender's balance and their fresh address. Analytics services spend months gathering such data bit by bit, but the counterparty gets it for free: they know your name and remember exactly what you paid for.
The change problem in the UTXO model
Bitcoin does not store a balance as a single number. The wallet operates with a set of unspent outputs (UTXOs), each of which is spent only in full. The difference is returned to a new address—this is the change. For example, when paying 0.01 BTC from cold storage with a UTXO of 0.41732190 BTC, the recipient sees: an output of 0.01 BTC, change of 0.40726190 BTC, and the network fee. A round amount indicates a payment, while the "tail" after the decimal point points to the remainder. Thus, an observer learns that the sender controls at least 0.41 BTC and can track the origin of the coins: if they came from a CEX, the owner has undergone verification.
How the "Exact Payment" mode works
The Mixer.Money service offers three modes, and the third—"Exact Payment"—fundamentally changes the scheme. Instead of returning coins to the sender, the agreed amount goes to the recipient from an exchange address, while the change is returned to the payer. The chain is broken at the service: the counterparty sees only a regular withdrawal from the trading platform, without your address or the size of the spent UTXO. This is fundamentally different from CoinJoin, where cooperative transactions with identical outputs are easily recognized by algorithms, and CEXs flag such coins as high-risk.
A key detail—the service does not accept exactly the invoice amount but sets a range. For a payout of 0.01 BTC, the request requires transferring from 0.0105 to 0.01575 BTC, i.e., the payment plus 5–57.5%. The specific value within the range is chosen by the payer. The fee is 4–5% plus a fixed 0.0007 BTC—at a rate of $64,000, this is about $45 regardless of the transfer size. On a 1 BTC payment, such a surcharge is negligible, but on a minimum request of $640, it eats up a noticeable share.
Practical steps
The process fits into five steps: prepare two addresses (the recipient's and your own for change, not on-chain linked to the sending one), agree with the other party on a payout time of up to six hours, create a request and verify the figures, send the coins in a single transaction within the specified range, and wait for the payouts. The change will also arrive from the exchange wallet, further anonymizing the history of your coins. No registration is required, and the request is valid for 168 hours. For each order, the service issues a guarantee letter with a PGP signature.
For everyday purchases, the mode is not suitable: the minimum threshold of 0.01 BTC cuts off small payments. For amounts below the threshold, there are alternatives: manual coin selection (coin control) reduces the amount of data, and the Lightning Network hides change through invoices. In my view, "Exact Payment" is justified where the risk of exposing transaction history costs more than the 4–5% fee—for example, in large settlements with sensitive counterparties. For frequent small transfers, it is better to combine Lightning with a clean UTXO obtained through the "Full Anonymity" mode.