Taiwan's government says a quarter of former mainland Chinese nationals running in the upcoming local elections may not legally qualify, a problem for those candidates and a sign of tightening scrutiny over China ties.

• 25 people who were once Chinese nationals have signed up to run in Taiwan's local elections, one fewer than first reported after a data error was corrected.
• Four of them never handed in proof that they gave up their Chinese household registration.
• Seven more did hand it in, but less than 10 years ago — short of the waiting period Taiwan requires before someone can run for office.
• Taiwan's China policy body ruled in April that the 10-year clock starts only on the day the paperwork proving loss of Chinese registration is filed.

Outlook: Election officials are expected to finish ruling on who qualifies by mid-October, and several of these candidates will likely be disqualified.