The 23-year-old's success means she has to pay more than her friends to the taxman in the UK, which she admits made her angry.
She told Q magazine: 'Use the NHS, I can't use public transport any more, doing what I do, I went to state school, I'm mortified to have to pay 50 per cent!
'Trains are always late, most state schools are s*** and I've got to give you like four million quid, are you having a laugh?'
The Someone Like You hitmaker added: 'When I got my tax bill in from [first album] 19 I was ready to go and buy a gun and randomly open fire.'