https://taler.net/ Taler technology: About taxability, change and privacy One of the key goals of Taler is to provide anonymity for citizens buying goods and services, while ensuring that the state can observe incoming transactions to ensure businesses engage only in legal activities and do not evade taxes (such as income tax, sales tax or value-added tax). However, we also want to stay out of the immediate personal domain, so sharing funds within a family or copying coins between devices should not be subject to monitoring by the state. In Taler terminology, we distinguish between transactions where the exclusive ownership of the value of a coin is passed from one entity to another, and sharing whereafter control over a coin is shared by multiple electronic wallets (which may belong to different individuals). In Taler, the receiver of a transaction is visible to the state and thus can be taxed, while sharing is invisible to anyone not involved. Once a coin is shared among different individuals, any one of those can try to spend it, but only the first spender would succeed. Thus, sharing requires a strong trust relationship among the individuals involved, and thus represent interactions in the protected immediate personal domain, and not commercial transactions. When Taler needs to provide change, for example because a customer only has a 5 Euro coin but wants to make a 2 Euro purchase, it needs to create fresh coins (of a total value of 3 Euros) that are unlinkable to the original 5 Euro coin to ensure privacy. To ensure that the resulting refresh operation where the change is converted to fresh coins cannot be used to transfer funds from one entity to another, Taler ensures that any owner of an original coin that was involved in a refresh operation can follow a link to the private information of the fresh coins generated by the operation. As a result of this trick, refresh operations cannot be used to create transfers, as the linkage ensures that the fresh coins are always shared with the owner of the original coin. As a result, Taler does not intrude into the personal economic domain, offers good privacy, taxability for transactions and the ability to give change.