The TCA allows the consumer to direct monies from a variety of sources to pay transaction charges. When a merchant agrees to accept payment through this service they agree to be bound by the terms and provisions of the META Assurance Agreement, which is similar to a credit card merchant agreement.
An incentive program is available to the merchants that uses a special unit called a "tan" (transaction account numerator), nominally equivalent to one US penny. The tan is used to drive commerce into the most efficient methods by adding value that can be tracked within the META system. There is no value difference between tan and other monies except that the tan is usable only in electronic transactions with participating merchants.
The tan is expressed as a superscript small "t" and can be combined with metric units to express larger values such as gigatan gt, ($10,000,000), megatan mgt ( $10,000), or kilotan kt ($10)