There will be a new 409a value following the round. The 409a value is the price of common shares that an independent valuation firm determines. An increasing 409a means that future stock options will have a higher strike price. For existing option holders who have options but haven't exercised, a rising 409a means a larger tax bill.

If the option holder decides to exercise, they will have to pay tax on the spread between the strike price and the 409a value at the time of exercise. This can be painful if the 409a value jumps significantly. There are a few companies like Uber, Airbnb, etc where the price jumped so much that many employees were stuck with massive tax bills.

If you find yourself in a similar situation, some funds like the ESOFund can help cover the up front cost and allow you to keep future upside.