Only 326 of the territory's 181,600 civil servants have signed up for the experimental pay-as-you-earn income tax launched at the beginning of this year. But Agnes Sin Law Yuk-lin, an Inland Revenue assistant commissioner, said the response was satisfactory and that it was too soon to say whether the scheme was a success. The experiment allows all civil servants to buy tax reserve certificates directly from their monthly pay packets, which will then be credited against their income tax bills. The 'pre-paid tax' earns interest and government officials said up to 20,000 civil servants could opt for it without the installation of extra computing resources. Mrs Sin said the Government would continue its publicity drive and consider plans to expand the scheme to those receiving civil service pensions.