What is an RSU?

An RSU is a restricted stock unit. The only difference between RSU and restricted stock is that an RSU is an unfunded promise. This amounts to an entry on the books at the corporate level. The only distinction between traditional restricted stock and an RSU is that you cannot make a Section 83 b election – the election for the employee to opt out of the standard IRS treatment with an RSU. Instead, you are typically taxed when the substantial risk of forfeiture goes away. 

There two key questions when evaluating the value of an RSU (1) when the does the earning period begin and (2) when does the earning period end.