(Updates to reflect December 2024 shutdown threat)

By Andy Sullivan

WASHINGTON, Dec 18 (Reuters) - U.S. government services

would be disrupted and hundreds of thousands of federal workers

would be told not to work if Congress fails to extend funding

past Friday.

Workers deemed essential would remain on the job. All

federal employees' pay could be disrupted during a shutdown,

though they would receive retroactive pay once government

operations resume.

Here is a guide to what would stay open and what would shut

down, according to agency shutdown plans outlined last year:

WHEN AND WHY WOULD THE GOVERNMENT SHUT DOWN?

Congress writes detailed spending legislation for most U.S.

government agencies each year, but it rarely gets the job done

before the fiscal year starts on Oct. 1. Lawmakers typically

pass stopgap spending bills to avoid disruption for several

weeks or months while they finish their work.

The current stopgap bill is due to expire on Dec. 20.

Republicans who control the House of Representatives and

Democrats who control the Senate have negotiated a 1,500-page

bill that extends that funding until March 14, when

President-elect Donald Trump will be back in office. But Trump

on Wednesday urged lawmakers to vote against it, complicating

its chances of becoming law.

If Congress does not pass some sort of extension and

Democratic President Joe Biden does not sign it into law before

midnight on Friday, wide swaths of the government would not have

the money to continue their operations in the days leading up to

Christmas on Dec. 25.

DOES THE MAIL GET DELIVERED IF THE GOVERNMENT CLOSES?

The U.S. Postal Service would be unaffected because it does

not depend on Congress for funding.

WHAT HAPPENS TO SOCIAL SECURITY, MEDICARE AND OTHER

BENEFITS?

The Social Security Administration would continue to issue

retirement and disability benefits.

Payments would likewise continue under the Medicare and

Medicaid healthcare programs.

Military veterans' benefits and medical care would also

continue.

Food benefits through the Supplemental Nutrition Assistance

Program and other nutrition programs would continue, though they

could be disrupted to some extent.

WHAT DOES A SHUTDOWN MEAN FOR THE MILITARY?

The 2 million U.S. military personnel would remain at their

posts, but roughly half of the Pentagon's 800,000 civilian

employees would be furloughed - ordered not to work.

Contracts awarded before the shutdown would continue, and

the Pentagon could place new orders for supplies or services

needed to protect national security. Other new contracts,

including renewals or extensions, would not be awarded.

Payments to defense contractors such as Boeing ( BA ),

Lockheed Martin ( LMT ) and RTX, formerly known as

Raytheon, could be delayed.

The Department of Energy's National Nuclear Security

Administration would continue maintaining nuclear weapons.

HOW DOES A GOVERNMENT SHUTDOWN AFFECT LAW ENFORCEMENT?

Agents at the FBI, the Drug Enforcement Administration and

other federal law enforcement agencies would remain on the job,

and prison staffers would continue to work.

The Secret Service and the Coast Guard would also continue

operations, and most employees would continue to work.

Most of the Federal Trade Commission's consumer-protection

workers would be furloughed, as would half of its antitrust

employees.

WILL NATIONAL PARKS CLOSE DURING A SHUTDOWN?

National parks, monuments and other sites would be closed to

the public, though it will be impossible to keep visitors out of

many of them. Rangers would be furloughed and restrooms, help

desks and other facilities would be shuttered.

Some states may use their own money to keep parks and other

sites open, as happened in the 2018-2019 shutdown.

Wildfire fighting efforts would continue, though timber

sales on national forest lands would be curtailed and fewer

recreation permits would be issued.

WHAT HAPPENS TO BORDERS AND HOMELAND SECURITY?

Most Border Patrol and immigration enforcement agents would

continue to work, as would most customs officers.

Local governments would not get new aid to shelter migrants.

The Cybersecurity and Infrastructure Security Agency would

suspend security reviews that help schools, local governments

and other institutions defend against ransomware.

WILL FEDERAL COURTS STILL BE OPEN DURING A SHUTDOWN?

Federal courts could operate for several weeks without

congressional funding, relying on fees and other funds, but

eventually would have to scale back activity. The Supreme Court

would stay open as well.

Criminal prosecutions would continue. Most civil litigation

would be postponed.

DOES CONGRESS STILL GET PAID?

Lawmakers would continue to collect paychecks, even as other

federal workers do not. Staffers would not get paid, though

those deemed essential would be required to work.

DOES A SHUTDOWN IMPACT TRANSPORTATION?

Airport security screeners and air-traffic-control workers

would be required to work, according to recent contingency

plans, though absenteeism could be a problem. Some airports had

to suspend operations during a shutdown in 2019 when traffic

controllers called in sick.

The Transportation Security Administration would not be able

to hire new airport security screeners during the busy holiday

travel season.

Some major infrastructure projects could face delays because

environmental reviews and permitting would be disrupted,

according to the White House.

WHAT'S THE IMPACT ON FOREIGN AFFAIRS?

U.S. embassies and consulates would remain open. Passport

and visa processing would continue as long as there were

sufficient fees to cover operations. Nonessential official

travel, speeches and other events would be curtailed.

Some foreign aid programs could run out of money as well.

WOULD A SHUTDOWN DISRUPT SCIENCE?

Scientific research would be disrupted as agencies like the

National Institutes of Health, the National Science Foundation

and the National Oceanographic and Atmospheric Administration

would furlough most of their workers once they run out of

funding.

NASA would continue to support the International Space

Station and track satellites, but 17,000 of its 18,300 employees

would be furloughed.

Weather forecasts and fisheries regulation would continue,

as would patent and trademark reviews.

The Federal Communications Commission would suspend

consumer-protection activities, equipment reviews and licensing

of TV and radio stations. It would continue to distribute

telecommunications subsidies and its broadband mapping effort.

WHAT HAPPENS TO HEALTH PROGRAMS?

The Centers for Disease Control and Prevention would

continue to monitor disease outbreaks, though other public

health activities could suffer as more than half of the agency's

workers would be furloughed.

The National Institutes of Health would furlough most of its

staff and delay new clinical trials for medical treatments.

Healthcare services for military veterans and Native

Americans would continue.

Most inspections of hazardous waste sites and drinking water

and chemical facilities would stop.

Food-safety inspections by the Food and Drug Administration

could be delayed. However, the FDA's testing of new drugs and

medical devices would continue.

WHAT HAPPENS TO THE SEC AND FINANCIAL REGULATION?

The Securities and Exchange Commission would furlough

roughly 90% of its 4,600 employees and suspend most activities,

it said last year, leaving only a skeleton staff to respond to

emergencies.

Likewise, the Commodity Futures Trading Commission would

furlough almost all of its employees and cease most oversight

activity.

The Federal Reserve, the Federal Deposit Insurance

Corporation and the Office of the Comptroller of the Currency

would continue as normal because they are funded by industry

fees rather than congressional appropriations.

The Financial Industry Regulatory Authority, an

industry-financed brokerage oversight body, would continue to

operate.

The Treasury Department would continue to issue debt and

manage the government's cash position.

DOES A SHUTDOWN DELAY KEY ECONOMIC DATA?

The publication of major U.S. economic data, including

employment and inflation reports of critical importance to

policymakers and investors, would be suspended.

WILL THE IRS STAY OPEN DURING A SHUTDOWN?

The Internal Revenue Service would stop examining and

auditing tax returns and responding to taxpayer queries.

Automated tax collection would continue, as would processing of

green-energy tax credits under the Inflation Reduction Act.

Roughly two-thirds of the agency's 90,000 employees would be

furloughed.

DOES THE SHUTDOWN AFFECT EDUCATION?

Pell Grants and student loans would continue to be paid out,

but could be disrupted as most Education Department employees

would be furloughed.

A protracted shutdown could "severely curtail" aid to

schools, universities and other educational institutions, the

department said last year. It also could delay funds that are

due to be awarded later in the year.

WHAT HAPPENS TO HEAD START AND CHILD CARE?

The White House said last year that 10,000 children from

low-income families would lose access to the Head Start

preschool program.

DOES A GOVERNMENT SHUTDOWN AFFECT SMALL BUSINESSES?

The Small Business Administration would not be able to issue

any new loans, though loans for businesses hurt by natural

disasters would continue.

HOW DOES A SHUTDOWN AFFECT FARMERS?

Meat and egg inspections would continue, but some lab

services would be disrupted, making it harder to fight animal

diseases. Crop insurance would not be affected, but some loan

programs would be. Research, conservation and rural development

programs would be shut down.

DOES A SHUTDOWN AFFECT WORKPLACE SAFETY?

Workplace safety inspections would be limited, and

investigations into unfair pay practices would be suspended.

The ability of the National Labor Relations Board to mediate

labor disputes would be curtailed because almost all of its

1,200 employees would be furloughed, according to a 2022 plan.

HOW DOES A SHUTDOWN AFFECT HOUSING?

Monthly subsidies for public housing and low-income housing

aid would be at risk. The Federal Housing Administration would

continue to back insured mortgages, and Ginnie Mae would

continue to back the secondary mortgage market. New homebuyers

in rural areas would not be able to get loans from the

Agriculture Department.

HOW WOULD A SHUTDOWN IMPACT THE WHITE HOUSE?

In the 2018-2019 shutdown, the White House furloughed 1,100

of 1,800 staff in the Executive Office of the President. Some

offices, such as the National Security Council, continued at

full strength, while others like the Office of Management and

Budget were scaled back sharply.

The U.S. Constitution specifies that the president continues

to get paid.