[The Washington Post]

Welcome to Health Reform Watch, Sarah Kliff’s regular look at how the Affordable Care Act is changing the American health-care system — and being changed by it. You can reach Sarah with questions, comments and suggestions here. Check back every Monday, Wednesday and Friday afternoon for the latest edition, and read previous columns here.

Obamacare hit a pretty important milestone this weekend: The law is now 100 days away from its main provisions coming into effect. That means the administration is pretty much in an all-out sprint to set up an infrastructure by which millions of Americans will soon purchase insurance coverage.

A potential approximation of an Obamacare summer to-do list? (Jahi Chikwendiu/The Washington Post)

It’s hard to understate the enormity of the task at hand for the Obama administration. It will be orchestrating the largest expansion of private health insurance in the country’s history. That means there’s a huge amount of work to be done over the next few months. There are at least 99 things that need to happen between now and October, and I’ve got a list to prove it. Much of this is informed by the Government Accountability Office report that came out last week, on the next big steps that need to happen on health exchanges. Some are big, some are small but all are pretty necessary to making the law work.

Here they are: