So what are we looking at?
Here is an example of how I organize my budget on shows. I start out with the title of the project at the top, followed by six columns. Date, Item (Category), Description, Price, Payment Method, Running Total. This is an example of an in-use budget for a not-yet-open show.
You need something that is easy to read. You are not the only one who will read this. If you have an assistant, they will have this in their lives. Producers will look at this or at least their assistants will. It is important to keep it organized and detailed. Once the Producer sees this paperwork though, there will be no more future expense estimation highlighted section and the total I have used will be noted down in the lower right hand side.
It is also important to notate how things were paid. If my assistant had paid for something with his own credit card that would be notated so I would know I needed to reimburse him. If the company you are working for has a company card it is important to notate that too.
Pro tip: Scan all your receipts into any receipt app so you have a backup. I use drop box because their black and white scanner is great!