You won't need Black Scholes for these. Black Scholes is just a formula to estimate the value of a stock option. It doesn't say anything about when to allocate

You won't need Black Scholes for these. Black Scholes is just a formula to estimate the value of a stock option. It doesn't say anything about when to allocate expenses, that's governed by GAAP accounting rules. Under US GAAP, the value of stock-based compensation has to be recorded at the fair value at the date of grant, not date of vest. The date of vest is used to decide when the award shows up as an expense. If a company is public, the value of an RSUs is probably just going to be the trading price. Snap's RSUs were a little more complicated because the grant dates of the pre-IPO awards were before the company was public, so they had to estimate the grant date fair value at the time using third party valuations, recent stock issuances to investors, and internal valuation techniques. If you look at their initial SEC filing, Snap says it issued 169.9 million RSUs from April 2015 - December 2016, and estimated the values to range from $15.36 - $16.33. The weighted average value of those shares was $2.7 billion. That's valuation. Now let's talk expense recognition. Those awards only show up in the income statement as an expense once they are expected to actually vest, after subtracting out expected forfeitures. That's why only about half of the $2.7 billion I mentioned above showed up so far in their financial statements so far. The rest of it will show up over the next three years.