Biden’s budget kicks off a long and likely painful process on Capitol Hill.

The budget blueprint President Biden is releasing on Thursday is dead on arrival in the Republican-controlled House. But its presentation marks the beginning of a long and convoluted process in Congress to set a budget for the federal government and then fund it.

The president’s budget, traditionally submitted in January or February of each year, essentially amounts to a messaging exercise in which the White House outlines its policy priorities. But the Constitution vests the power of the purse with Congress, and it falls to lawmakers to approve the spending levels of government agencies and programs.

In theory, funding the government takes place in two major stages. First, lawmakers on the Budget Committees coalesce around a budget resolution — a blueprint laying out an overall spending ceiling and a revenue floor. Then, after Congress approves a budget resolution, it falls to lawmakers on the Appropriations Committees to allocate federal dollars, following the blueprint.

Here is a step-by-step overview of the process, and why it will be so fraught.

Step 1: The president submits his budget to Congress.

In addition to setting an aspirational top-line number, federal agencies prepare detailed documents outlining requests in support of their programs, projects and activities.

Step 2: Lawmakers draft and pass their own budget.

Theoretically, the budget committees in the Senate and House separately draft budget resolutions, setting their own top-line number and providing general contours for federal spending. However, in the past several years, lawmakers have skipped this step altogether, and congressional leaders, in collaboration with senior appropriators, have agreed on the overall numbers.

This year, Senate Democratic leaders have dared House Republicans to put forward their budget blueprint first, with the refrain: “Show us your plan.” It’s not clear whether Senate Democrats will ultimately even put out their own resolution.

House Republicans are toiling to agree on a plan to balance the budget in 10 years without touching Medicare, Social Security, or military spending — a gargantuan task that has left even some top party officials questioning how they will meet their spending objectives while keeping their members in line. Whether they can put together a resolution that can garner the 218 votes needed to pass — pleasing both hard-liners and more mainstream conservatives in competitive districts — remains to be seen.

If they manage to do so, that plan is all but certain to be rejected out of hand in the Democratic-controlled Senate.

Step 3: Appropriators allocate money to federal programs.

Once Congress has either approved a budget resolution or congressional leaders have agreed upon a top-line number, lawmakers on the Appropriations Committees will set spending levels for federal agencies on a more granular level, and codify them into appropriations bills to fund all aspects of the government.

In recent years, these spending bills have been lumped into one enormous piece of legislation referred to as an “omnibus” spending bill. But conservative hard-liners have pushed Speaker Kevin McCarthy of California to abandon that practice, so House Republicans this year say they intend to pass 12 separate appropriations bills divided up by federal function.

But those measures, too, are unlikely to be acceptable to the Democratic-controlled Senate, given that Republicans are proposing huge cuts.

Step 4: Presidential signature or government shutdown.

The president must sign spending bills by Oct. 1, the start of the fiscal year, to fund the government. If Congress fails to agree on them, lawmakers must either extend the current year’s spending levels while they work out their differences, or funding lapses altogether, leading to a shutdown.

The consequences of failing to come to an agreement on the federal budget are even graver this year, because a critical bloc of House Republicans have said they will only vote to increase the debt ceiling if Democrats agree to deep budget cuts.

Because the United States borrows huge sums of money to pay its bills, failing to increase the government’s legal borrowing limit could plunge the economy into crisis, prompting a first-ever federal debt default. Officials have predicted the limit will be reached this summer.