Every year my books get slightly better. This year I want to tackle discount received...or should I?

I have in the past just split what I have paid for stock into what I paid for it and delivery and made no note of discount received. Unfortunately when I use my pos system I just enter the invoice amount for the product, not for instance R100 less 3%, otherwise there would be quite a bit of working out. Therefore my stock value on my POS is probably a little higher than my book value – although they are treated as separate systems in my shop.

Should I be working out individual prices or should it reflect as income? I will probably go on the new small buss tax so this is probably a moot point, but just for the record….and I plan to take my turnover above 1 mill in the next couple of years