When I use the caluclator, I have the following concers.
1. It gives me some 200,000 allowances. Is it applicable to all, or only hong kong residents ?
2. It asks whether married or single, if married, does it required the wife should be in Hong Kong?
Do keep in mind that around 70% of the people in HK do not pay taxes and HK$20K is below the median earnings, so I'd be surprised if you had to pay taxes.