Can I buy the iPhone 6S from UK and get a tax back refund?

I'm going to London next week and the date will be same as the new iPhone 6S release date. I'm wondering if I buy the iPhone from there how much will be the tax back like in percent usually?

and how can the tax back be done?

I do not know how the taxes are

If you're from outside an EC country and are permanently exporting the phone, you can reclaim the VAT (Value Added Tax) element of the price you pay. In the UK the rate of VAT on your phone will be 20%. UK retail prices include VAT so as an example, a £600 phone will include £100 of VAT which you can claim back.

The way it works is that you buy from a supplier who is able to provide a VAT 407 form at the time of purchase. In theory, all retailers should be able to do it but in practice only those who are used to dealing with foreign visitors are familiar with the process. So that means airport shops, and those in busy central city shopping areas such as central London. Expect to be asked to show your passport and possibly proof of your address to prove your eligibility; it takes the retailer time to complete their part of the form so they don't wish to waste it on those who aren't eligible such as EC citizens and non-EC citizens domiciled within the EC. You then need to allow extra time at the airport to claim back the VAT; you complete your part of VAT 407 and present it to UK Customs and Excise along with the purchase receipts and the exact goods upon which you're claiming the tax refund. If you meet the conditions an immediate refund is issued. Note that at some UK airports you may need to allow time to visit the Customs Office at a different departure terminal to one you're flying from, and that they're not open 24/7 so check and plan ahead.

If the refund process seems a bit inconvenient and awkward then it's hardly surprising. It costs the Government money to make refunds and the refund itself is a loss of revenue. Those costs are proportionately far higher for piddly little refunds so many buyers balance the time and effort they need to invest themselves in claiming a refund against the likely size of the refund. So you aren't likely to want to arrive at the airport many hours earlier than you originally planned and perhaps have to travel to a different departure terminal if all you'll get back is £20 or so. But for sums of £100 or more it's usually considered to be worthwhile.

There are other ways to claim the refund but the above is the normal method.