Recently, the Shanghai immigration authorities have changed their policy on issuing Z (work) visa invitation letters to foreign nationals in Hong Kong, and have also made some tougher decisions about whether M (business) visa holders are legitimately travelling for business.
Z Visa Applications in Hong Kong
The Ministry of Public Security in Shanghai has recently stopped issuing invitation letters for foreign nationals to obtain Z (work) visas in Hong Kong, unless the applicant has a Hong Kong ID Card (which establishes residency). Previously, it was possible to obtain a Z visa for Shanghai in Hong Kong without a Hong Kong ID Card.
Other Chinese cities may still issue Z visa invitation letters for foreign nationals in Hong Kong with no Hong Kong ID card, but this should be checked on a case-by-case basis.
M Visa Holders
The immigration authorities in Shanghai have recently turned away some frequent business visitors holding M (business) visas at the border.
The explanation seems to be that, although the visitors were on legitimate M visas, the frequency and length of their visits suggested to immigration officials that they weren’t genuine business visitors, but were actually coming to China for work.