How to create a Visual BASIC software for billing department?

Answer 1

To do this is a major undertaking that could not be answered in this answer. To write any kind of system you need to do some analysis and design to find out what exactly is needed and how you are going to do it. Only then can you start to actually create your forms and your Visual BASIC code. There are many other elements you would need, like data storage files. So it is a major undertaking, well beyond a simple answer.