UK Query on Revenue figure when using Flat rate VAT

[Secondtrader]

My understanding is the Revenue figure excludes VAT. I am on the VAT Flat Rate Scheme paying 10%.

So I invoice a customer showing a cost of £100 net plus 20% VAT giving a total cost to the customer of £120. Under the Flat Rate Scheme my VAT liability Is 10% of the £120 = £12.

So is my Revenue figure the £100 or £108 (£120 - £12 Flat Rate VAT)?

Many thanks.