Budget management is a big part of Adarian Money for Palm OS, a complete personal finance program for Palm-powered handhelds. To start managing your budget, simply define a few categories (or sub-categories) such "Auto", "Auto : Fuel", "Auto : Service", ..., etc:

Then, assign each month's budget and alert levels: (Alert levels are usually a little lower than the budget, so that when the actual expense is over the alert level but not the budget, you still can get a heads-up alert.)

Now, whenever you enter a new expense or modify an existing one, the program would check the total actual expense on that category. If it's over the budget or the alert level, an alert would be issued automatically:

Budget Roll-Over is a feature that when there is unused budget in a month, you can carry it over the to the next month so that next month's budget becomes higher.

To get a better view of this month's (or any period's) budget situation, you can go to the Categories/Budget view. This view tells you the budget of each category, how much has been spent, how much is left, and the percentage.

Also, in the Current Status view, which displays the overall current financial status, there is a section that shows which categories have been over the budget you set (in bold letters), or over the alert level (in normal letters).