For each job, you can specify whether the price includes VAT, excludes VAT or is not VAT-able (no VAT).
So for example:
if the price is £10 inc VAT, you would charge £10, and keep £8.51 net after repaying the VAT to HMRC
if the price is £10 ex VAT, you would charge £11.75, and keep £10 after repaying the VAT
if the price is £10 no VAT, you would charge £10 and keep £10, nothing to HMRC (not sure you could ever do this as a VAT registered window cleaner though!?!?!)
Aworka obviously does all the sums for you and puts the right amounts in the right places.