It’s not easy to sell a privately held tech company these days. But the real headaches sometimes begin after the deal closes, according to a new study by Shareholder Representative Service, which manages the post-closing process in M&A transactions for its clients.

The post-closing period can be “long, risky, and complex,” the study found. Claims related to deals can be filed over an extended period of time, even after closing. Meanwhile, shareholders are increasingly demanding that certain conditions, such as performance goals, be met before the privately held company can cash out.