- Office systems, or self-made systems. As a rule such systems are developed by one or several developers who used to work in a company which had a billing system. These systems can be characterized by an office operating system, database, open source code, growth by random accretion, errors in calculations, non-optimal structure of data storage, and replicates of report forms with unknown retrieval algorithm. Such systems are often custom made the customer sets the task, as a rule, without deep systemic analysis. Using of such systems often results in losses either direct or in form of lost profit.
- Industrial systems. These systems operate 24/7 without errors and fault regardless the number of serviced bills. Usually such systems are built on an industrial OS and DBMS developed by a large number of developers, they also have lots of installations. These systems usually have advanced administrative tools, systematized reports, built-in detailed help reference. Unfortunately, large number of copies and application of an industrial DBMS are not enough to consider a system to be an industrial one and a client is not free from problems while using such system. The efficiency of any system can be reduced by the following factors: incorrect task setting, not-optimal structure of data storage and inconvenient interface.