The main advantage of open source billing software is that it can help your business succeed. Open source billing software has the ability to adapt to your business. Basically, you, as the administrator of the site can control how/when everything is done. Open source gives your company the ability to change the overall look and feel of the site. You also have the opportunity to change how your business runs. Businesses change over time, sometimes they blossom, sometimes they falter, although no one wants the latter it is a smart idea to have software that is agreeable to your financial needs.