Around 200 ICAC officers were deployed in major operations, codenamed Hover and Sky Horse, resulting in the arrests, which included eight Inland Revenue Department (IRD) officers and a former assistant assessor. Operation Hover spanned three months and uncovered organised corruption involving officers allegedly pocketing everything from monthly HK$10,000 bribes to free trips to visit dens of iniquity in China or Macau in return for their assistance.

The former IRD assistant assessor is alleged to have secured more lenient penalties for various companies subject to IRD investigation, including one company accused of profit understatement and suspected of being heavily involved in smuggling activities. It is further alleged that he shared a HK$250,000 "reward'' with a certified public accountant (CPA) and bank manager - both of whom have been picked up as well - for aiding the company. Despite having left the IRD in June last year to work as a tax consultant with a firm of accountants, investigations revealed the former assistant assessor "continued to secure the corrupt assistance of seven serving IRD officers in relation to the tax cases of at least 50 companies''. This involved passing on copies of documents from IRD files and checking internal computer systems.

In the second case of corruption, uncovered in Operation Sky Horse, the eighth serving IRD officer, an assistant taxation officer (ATO), allegedly accepted about $80,000 in bribes for assisting nine companies and 12 individuals to avoid penalty or prosecution for late submission of tax returns.

The arrests have prompted the Inland Revenue to call for an "immediate review of internal checks and controls." Acting Deputy Commissioner of Inland Revenue Alice Lau Mak Yee-ming said the department would not tolerate or condone acts that compromised the protection of taxpayers' information.

Under the Prevention of Bribery Ordinance, a government officer convicted of corruption faces a maximum fine of $500,000 and seven years' imprisonment.