NAV was one of the first ERP systems to fully implement a multi-currency system. Transactions can start in one currency and finish in another. For example, we can create the order in US dollars and accept payment for the invoice in Euros. For this reason, where there are money values, they are generally stored in the local currency (referenced as LCY) as defined in the setup. There is a set of currency conversion tools built into the applications and there are standard (by practice) code structures to support and utilize these tools. Two examples of code segments from the Sales Line table illustrating handling of money fields follow:

In both cases, there's a function call to ROUND and use of the currency specific Currency. Amount Rounding Precision control value.

As we can see, before creating any modification that has money fields, we must familiarize ourselves with the NAV currency conversion feature, the code that supports it, and the related setups. A good place to start is the C/AL code in Table 37 – Sales Line, Table 39 – Purchase Line, and Table 330 – Currency Exchange Rate.