The definition of capitalizable expenses tends to be the same between GAAP and tax. The depreciation schedules are frequently different.
Yes, it tends to.
However: https://www.law.cornell.edu/uscode/text/26/174
any amount paid or incurred in connection with the development of any software shall be treated as a research or experimental expenditure [and be capitalized and amortized over five years even if it is disposed of, retired, or abandoned]
I stand corrected. I've not seen GAAP vs IRS differ so much in my experience. Thanks for referencing IRS section 174 which clears things up. It appears to be quite strict on the 5/15 year amortization of software development expenses, and I now agree with OP that the change to section 174 as part of the TCJA is some bullshit.