Sen. Bernie Sanders (I-VT) has reintroduced his Medicare-for-all bill, which would create a single-payer health care system in the US.

The proposal, which Sanders also introduced in 2017, establishes a government-run health care system that covers all Americans. The plan would allow patients to visit doctors with no out-of-pocket fees. The inclusive coverage would only require patients to pay for prescription drugs.

Yet there is one question that haunts all single-payer systems: How do you pay for it? Sanders says he has an answer, or many answers. His proposal includes a list of financing options, including different ways of taxing the wealthy. (It’s not uncommon for single-payer systems to shift costs to the wealthier.) But if the bill were to become law, Congress would have to pick from among these options to pay for it — and that’s where attempts in other countries (and Vermont) to create single-payer systems have sometimes faltered.

Read Sanders’s full bill here or below: