The Immigration Department are very strict about people who overstay their visa in Hong Kong.
If you are a visitor here and find yourself a day or 2 accidently overstaying, and have a good reason for this oversight, you may very well be able to sort it out at the airport as you depart.
However, you must appreciate that it is not recommended that you allow this to happen, nor that the Hong Kong ID will be happy with this sorry state of affairs.
In every other case, you must immediately report to Immigration Tower in Wanchai as soon as you realize that your current limit of stay has expired – visitor or resident alike.
The Hong Kong Immigration Department take the question of visa overstayers very seriously indeed – and long term overstayers could find themselves incarcerated for a period before being removed from Hong Kong – so under no circumstances should you allow an overstay to happen.
If you are a resident and have a genuine reason for slightly overstaying your visa (say because you’ve been in hospital) and there has been no-one around to help you sort your visa out, you can expect that the Department will be sympathetic and happy to help.
But everyone has a legal obligation to remain in Hong Kong subject to all their conditions of stay, including the limit or time imposed, and if you breach this, the consequences can be very serious indeed.
So please, take your visa expiry date as sacrosanct and plan your lives here around the immigration permissions you have been given – including the time allowed to stay.