If you buyout within 30 days of lease inception, then the easiest way to compute the adjusted lease balance is as follows…
adjusted lease balance = (adjusted cap cost - 1st base payment) x (1 + RATE)
Your buyout is the adjusted lease balance plus any applicable taxes and fees.
The 1st payment is due at lease signing in which the entire amount is treated as a depreciation payment. However, interest (rent charges) is always levied one month in advance.
See my post for more details…