The Question is about :-
Subject: Documents and Expenses

Question: I am employee and have been asked to put together a database to handle administrative documents. 
The database has to be able to keep track of expenses and employee travels. 
Some of documents the receptionist looks after are the following invoices, 
contracts, purchase orders/requisitions, travel expenses/authorizations, statements. 
I was able to come up with data model for this database but I am stuck because 
invoices can be from a project or a contract or a purchase order, and statements have accounts. 

I don't know how to include information on projects or accounts within the design. 

So far i have the following tables Documents Document_Types Invoices Statements Contracts 
Purchase_Orders Travel_Authorizations Travel_Expenses Budget_Codes Suppliers 

I would like this database to be able to track all the office expenses using the budget 
codes year to year. 

Any help you provide would be greatly appreciated.