In the 1990s there were several attempts to make accounting software for LETS using databases on local machines. The most valiant attempt at intertrading using Access was in Scotland where everyone was using a well developed MS Access application called SAM. The LETS of LETS was held in a separate instance of SAM and transactions were communicated by email.
Around 2003 CES arrived, a web service allowing LETS to have their own web site in which members managed their own accounts rather than processing cheques communicating by post. CES grew quickly when it offered an intertrading mechanism between exchanges. A fixed exchange rate was calculated according to the national currency and the time-value of each exchanges unit, and this persists to this day.
The author of this document and CTO of Community Forge attempted to improve the CES system with an open API and in 2012 but the task was too onerous. Several LETS around Zurich are networked together with a semi automatic system which requires they all use the same platform.