Can I use my own business expense categories?

I am using TurboTax for Business for the first time.  I have an S corp, and I am the sole shareholder and employee.  I have been categorizing my business expenses in a spreadsheet, but my categories are different than I see in TT.  If I change all my categories to match TT it will be a fair amount of time and effort.  Can I simply use the categories I have, which have been working for me for many years?  Will it raise a flag with the IRS if my categories are different than TT's?