I am not the calculator you remember. Now you make your own keys. Make a key called VAT and give it 18. Make a second key called gross and write what it does: the number on the screen, plus VAT. Type 36,000, press gross, and you get 42,480. Next year VAT changes? Change that one key. Every key that uses it follows, the way a cell does in a spreadsheet. Your keys stay on your device, and you can send them to someone as a link.