MANY official company charges could double if the Government's proposed new Companies Registry is to survive as a ''commercial'' semi-autonomous body. The remainder of the Registrar-General's Department is to be dismantled on April 1 and replaced by a separate Lands Registry and Companies Registry. Both will be self-supporting bodies, adopting Governor Chris Patten's new spirit of commercialisation within the civil service. Assuming the Trading Funds Bill is passed by the Legislative Council in the spring, the two bodies are set to become the first government departments to adopt what has been dubbed ''trading fund'' status in Hongkong. Under the standard system of ''vote-funding'', department expenditure budgets are voted on by Legco. Under the trading fund system, the two new departments will operate independent accounts, oversee their own spending and be run with some private-sector management style. However, they will remain accountable to Legco, the Financial Secretary and the Governor, and any large surpluses might be passed over to government coffers as one-off payments. If the experiment is a success, other fee-charging government departments which produce regular surpluses could follow suit. Observers say the Electrical and Mechanical Services Department, Information Technology Services Department, and the Land Transport Agency are prime candidates. The fee-charging services to be offered by the Lands Registry are likely to make it quite profitable. But the Companies Registry is not expected to be able to generate enough income for the department to keep its head above water if it keeps charges at current levels. Outgoing Registrar-General Noel Gleeson, who will retire after his department is disbanded, warned at a press conference yesterday that the body could quickly slip into deficit unless fees were radically reviewed. The Companies Registry will levy dozens of relatively small, existing fees for services provided by the Registrar-General's Department. Mr Gleeson thought that, at their current low levels, these charges were fairly insignificant for businesses. He thought they generally could be doubled without causing too much pain. The fee for filing annual returns, for instance, has been $50 since 1988; the fee for filing of changes in particulars of directors has been $10 since 1984; and a certificate of incorporation of a company has been $100 since 1989.