Hey I found this online vat calculator a few days back and this does pretty much the same what you explained in your comment, it's just that with this you just need to enter values and you will get calculated vat !.. you'll know exactly how much will be deducted and how much will reflect in your...
Please tell me more about your lighting store. i am the owner of smartgeekhome that is providing smart plugs, led bulbs, smart thermostats, ecobee thermostats and alexa almost including all type of smart home devices.