Calculating tax when there is an FYA

Good Afternoon! in an apv question, i have run into a tax issue in my cashflow setup. my method is to setup a workings table as follows: operational net cash flow (capital allowance) ----------------------------------- taxable cash flow then i apply the tax rate and then subtract these taxes in my main setup of cashflows. tax payments lag by one year. problem: my final cashflows for year 1 and the last year (yr 5) are wrong. (my computation of CA is correct and matches with the answer) in this example, there is an FYA and i am applying this to year Zero and calculating the taxable CF. not sure if this is correct. how do i use this method of minusing CA to cases where there is an FYA? ----------------------- please note, i have solved the issue by taking tax savings on the CA and adding them to the cash flows. but i do want to know how to use the above method thank u