Taiwan's stock exchange is cracking down on investors who fail to pay for shares they bought — bad news for traders who have been defaulting, and a move aimed at cleaning up a market that has seen too many failed settlements this year.

• The exchange's board approved rules stretching the default tracking window from one year to five years.
• A first default now means brokers must collect cash or shares up front for the trader's first 10 trading days once they are allowed back in.
• A second default within five years pushes that prepayment requirement out to 30 trading days.
• Separate rules will curb brokers from flooding the market with warrants, cutting the issuance quota tied to their capital and raising the floor on how many units must stay outstanding after cancellations.

Outlook: Repeat defaulters face far longer restrictions, and warrant supply should thin out as brokers work under tighter issuance limits.