But as a mature company, Amazon's stock price is not likely to undergo huge swings. Thus you wouldn't file an 83b. However, a startup aiming for unicorn status

But as a mature company, Amazon's stock price is not likely to undergo huge swings. Thus you wouldn't file an 83b. However, a startup aiming for unicorn status will have a huge inflation in valuation on the way to being a unicorn (and beyond). If you're unlucky, doing an 83b early exercise will hit right as the valuation jumps, leaving you with a five figure tax bill. I mean, that's better than, say, an eight figure tax bill, but taking a five figure risk so early on in a companies life cycle when there's not even a proven product market fit is, well, risky. If you're in a place where losing that kind of investment because of a remotely possible potential upside, your risk tolerance is simply higher than mine. The other thing to consider is your vesting timeline. As you vest, you'll owe additional taxes, which means a sizable tax bill before there's been a liquidity event. If you are rich enough to afford that then hey, go for it. But not everyone is in a position to be able to do that.