From Social Security to travel: Everything to know about a government shutdown

A government shutdown is on the horizon and could impact more than your ability to watch pandas play on the "Panda Cam" at Smithsonian's National Zoo.

Lawmakers have until the end of the day Saturday to reach a deal to keep much of the government open. If they fail, the U.S. will head into what would be one of the largest government shutdowns in history.

Here's what to know:

How did we get here?

Earlier this year, a group of Republican hard-liners in the House refused to raise the nation's debt ceiling until President Joe Biden and the Democratic-controlled Senate agreed to steep spending cuts.

The threat of economic calamity forced Biden to the negotiating table with Speaker Kevin McCarthy, and the two agreed to a spending cap for the upcoming 2024 budget year, which begins Oct. 1. But as the months passed, spending legislation remained mired in Congress with the hard-liners in the House insisting on curbing spending further and other proposals that couldn't pass the Senate.

This week, McCarthy and other House Republicans said they want Biden to agree on border restrictions.

"If he wants to keep the government open, he needs to shut down the border," Rep. August Pfluger, R-Texas, said of Biden. "No border security, no funding."

That idea is unlikely to survive with even the top Republican in the Senate -- Mitch McConnell of Kentucky -- scoffing at the idea, noting that a shutdown would yank pay from border patrol officers needed for better security.

What happens next?

One possibility is that McCarthy turns to Democrats to help him pass a spending bill, but that's unlikely. Leaning on Democrats would anger hard-liners in his party and possibly trigger calls to oust him as speaker.

More likely, a significant portion of the government will run out of money at midnight on Saturday, and some 4 million workers will stop getting paid, including military troops.

With a shutdown appearing imminent, federal agencies on Thursday notified employees that it's possible they will either be "furloughed" -- a government term for being laid off temporarily -- or "excepted" and required to report to work without pay.

Excepted workers are those needed to protect life and property, including law enforcement and military troops, but also civilians who tend to orbiting space craft, the power grid, federal prisons and airport security.

If a shutdown continues, the first possible missed or incomplete paycheck would be on Oct. 13 for many workers.

All federal workers are expected to get back pay when the shutdown ends, although union officials say that's not a good solution. In the last shutdown, air traffic controllers and security workers began calling in sick because they could no longer afford child care, gas and other expenses to get to work.

Many federal contractors such as janitors and security guards will be laid off too, without the promise of back pay.

What happens to Social Security in a shutdown? How will a shutdown impact me?

As disruptive as shutdowns can be to families of government workers -- and cost taxpayers more money in the end -- most Americans won't see a big difference right away.

That's because the vast majority of government spending is set on autopilot by Congress and will continue as "mandatory" spending. Also, hundreds of thousands of government workers will agree to show up without pay -- at least initially.

For example, payments from Social Security, Medicare and Medicaid will continue to reach mailboxes, although agencies warn services could slow down.

At the Social Security Administration, for example, officials say they will continue to ship out payments and people can still apply for benefits. But benefit verifications will stop, and people won't be able to receive replacement Medicare cards.

You should still plan on paying your taxes, but the IRS warns it will be responding to requests with only one-third of its staff.

The U.S. Postal Service also won't be impacted because it relies on its own revenue stream.

For the 27% of government spending that will be impacted, some critical programs such as disaster relief will limp along as government agencies move around cash. Another federal program that provides food assistance to low-income families called SNAP, should be available without problems through October. However, another program by the Agriculture Department that helps feed low-income mothers called WIC could run out of cash within days and waitlists could grow.

To most middle-class Americans, the most obvious impact will be at national parks and federal landmarks such as the Statue of Liberty, which will close unless state governments pay to keep them open. The Smithsonian buildings and its National Zoo will also close, and the zoo will turn off its "Giant Panda Cam," where Americans can watch the pandas play.

NASA will shutter its public television and coverage of live launches.

Trash could pile up in the federal parks outside the White House, Capitol Hill and other federal buildings, where janitors working for hourly wages under federal contracts will be sent home without pay.

Lawmakers will still take in their $174,000 annual salaries, but their staffs won't get paid, and Republicans won't be able to continue their impeachment inquiry into President Biden.

But the biggest impact will likely be on low-income families outside Washington, where 85% of federal workers live and work. If the shtudown lasts long enough, federal workers and contractors are likely to show up at food banks as they did in the last shutdown five years ago.

Longer lines at the airport and canceled flights are a possibility too if federal workers who direct traffic or screen luggage quit because of financial troubles and get jobs elsewhere.

Why is this shutdown different?

Shutdowns aren't uncommon. They've happened to varying degrees 20 times since 1977, according to the Congressional Research Service.

What's particularly remarkable about this shutdown is that lawmakers haven't agreed as of Friday on how to pay for military troops.

The last time military service members went without pay was in the 2018 shutdown when Coast Guard personnel were forced to work without pay. But that was mostly attributed to an oversight. Congress passed legislation in 2018 paying for the Defense Department, but the Coast Guard reports up to the Department of Homeland Security.

This time around, the Coast Guard is on track to be joined by the Army, Air Force, Space Force and Marines -- 2 million active-duty and reservists -- in potentially forgoing pay.

The last time those Defense Department personnel went without compensation was November 1995 in a five-day shutdown that ended before service members missed a paycheck. Troops quickly received back pay.

This time, there's no agreement in sight and it's unclear how long the shutdown could last.

ABC News' Luis Martinez and Gina Sunseri contributed to this report.