CHINA'S laws and regulations on personal income tax have become incompatible with the present state of the economy as a result of rapid development over the past decade, a mainland tax official says. Personal income tax in China is governed by three sets of laws and regulations: individual income tax law, provisional regulations on individual income adjustment tax, and provisional regulations on tax on self-employed people. When the individual income tax law was introduced in 1980, only a handful of Chinese nationals had to pay, said Shen Shanging, an official with the State Administration of Taxation. ''At that time, taxpayers were mainly foreign personnel and overseas Chinese,'' said Mr Shen. But as economic development continued, the income level of Chinese nationals also went up, with some becoming much richer than their compatriots, he said. An official survey in mid-1992 put the number of mainland millionaires at just over 500, but a year later the Chinese press offered the ''most conservative estimate'' of one million. Mr Shen said the existing three pieces of legislation each applied to a particular target: foreigners, ordinary Chinese and self-employed urban residents. Their co-existence resulted in inefficient implementation and was incompatible with international practice, he said.