Last paragraph:
http://www.hkclic.org/en/topics/ ... tity_cards/q3.shtml
"Under section 17C of the Immigration Ordinance , every Hong Kong resident who is aged 15 or above is required to carry proof of identity. This usually means an identity card. It is an offence to fail to produce proof of identity on demand to a police officer or immigration officer. However, in practice, persons are unlikely to be prosecuted if they are found without an identity card when they are near their home.
With respect to children, there is no obligation to apply for an identity card until the age of 11 ( section 17C of the Immigration Ordinance ).
Visitors who are staying in Hong Kong for not more than 180 days are not required to apply for identity cards ( regulation 25(d) of the Registration of Persons Regulations ). Nevertheless, such visitors are strongly advised to carry proof of identity (e.g. passports) with them, otherwise they may be detained by the police or immigration officers for verification of their status."