While Beijing has been busily damming up official channels for money to leave China, more than ever is leaking out through shady means as investors flee the country's slowing economy and weakening currency. China's official foreign exchange reserves fell more than half a trillion dollars last year and are still falling, with a loss of nearly $46 billion in October alone, and the

International Institute of Finance think-tank estimates outflows doubled in the September quarter to more than $200 billion. To stem the flows, Beijing has frozen or restricted its main schemes allowing wealthy individuals (QDLP) and financial institutions (QDII) to invest overseas, and lawyers have noted a sharp slowdown in the approval process for large overseas direct investment (ODI) deals."Fresh new QDII quotas have been broadly halted, ODI investments involving large amounts of foreign exchange remittance are taken on a case-by-case basis, and the QDLP scheme is undergoing a slowdown," said Yin Ge, counsel and head of financial services practice at Clifford Chance in Shanghai.

Industry executives say there is no likelihood of any thaw in the coming months, so investors are seeking other means to get their cash out, such as faking trade transactions through Hong Kong.

"The growth in the sheer volume of such transactions going through such channels means that even though more suspicious transactions are being caught by financial institutions, they represent a tiny fraction of the overall volumes of fake trade invoicing," said Alicia Garcia Herrero, chief economist at Natixis in Hong Kong. Official efforts to curb outflows have been extensive. Two executives at separate fund management companies in Hong Kong said the QDLP programme, halted since March this year, is likely to stay that way until mid 2017, according to briefings with government officials. For cross-border transactions above $50 million, government officials are demanding personal visits from investors to the offices of the State Administration of Foreign Exchange, the country's forex regulator, or asking them to pay by instalments.

And they are bearing fruit. Outbound Chinese mergers and acquisitions in the September quarter have fallen by more than half to $38.4 billion from the March quarter, according to Thomson Reuters data, and from $42.5 billion in the June quarter.