ELIGIBILITY rules for British Overseas Citizen (BOC) passports will have to be worked out by 1996 to make sure qualified applicants get hold of the document after Hong Kong reverts to Chinese sovereignty, according to Principal Assistant Secretary forSecurity Simon Vickers. Mr Vickers told the Legislative Council's nationality subcommittee yesterday that the Government had already written to alert Britain on the issue. He said the Government had recommended that Britain ensure applicants knew if they could obtain a BOC passport before 1997. Mr Vickers said the arrangement would not be equivalent to issuing the passports earlier as local BOC passports could only be issued after 1997. BOC status is offered to people who, having settled in an ex-British colony, are unable to become nationals of the place on independence and, therefore, end up stateless. ''The BOC is only a residual option for those who would otherwise be stateless on July 1, 1997,'' he said . Mr Vickers also told legislators that with the exception of Spain, all countries of the Schengen Convention had decided not to change their visa policy towards Hong Kong before a ministerial summit next month. Spain has decided not to wait until the summit and confirmed with the Government that, starting October 1, it will require visas from Hong Kong travellers. Under the Schengen Convention, nine of the 12 European Community members - Belgium, France, Germany, Greece, Italy, Luxembourg, the Netherlands, Portugal and Spain - will introduce a common visa policy in autumn. The new policy could mean the 3.5 millionBDTC and BNO passport holders are no longer entitled to visa-free entry to six of the countries.