This chapter explains the nature of trial balance (TB) working paper software. The primary function is to serve as a trial balance software application with direct links to all the supporting digital working paper files, as well as to link directly into a financial statement reporting application and to transfer the trial balance data directly into the tax software. The TB is typically presented in a spreadsheet-like format with the option to view it in the various iterations, for example, tax basis, cash basis, and so forth. In fact, the TB component may be presented in an Excel worksheet format. Working Paper Binder is the feature that really distinguishes this application from typical TB software, the ability to have a structured repository for all the files that support the TB, such as PDF files, e-mail messages, Excel spreadsheets, Word documents, and so forth. Tax Software Bridge is a very important feature for entity tax engagements.