# Tracking Documentation on Accounting Transactions While [[double entry accounting|UseCases/DoubleEntryAccounting]] transactions are the heart of any accounting system, auditors and managers need the ability to dig down and determine what contracts, invoices, receipts or other backup documentation relate to a given accounting document. An adequate accounting system should provide easy link-up between double-entry accounting transactions and the documentation that relates to the transactions. For example, [[expense reports and reimbursement requests|UseCases/ReimbursementRequest]] often have a myriad of receipts and invoices associated with them. [[Handling contractors|UseCases/ContractorsAndContracts]] has similar types of backup documentation. Ideally, the system should allow the exploration of and linkage to documentation in both directions. It should be trivial to answer questions such as: * I have this receipt/invoice from our document repository. Which accounting transactions relate to this receipt? Has the transaction been [[reimbursed|UseCases/ReimbursementRequest]]? * Looking at this invoice, can I see the transaction where it was accrued and paid? * Show me a list of invoices that haven't been paid, with links to those invoices. * Who approved this expense or payment? Show me the email where they approved it.