(Reuters) – A shutdown of about a quarter of the U.S. government reached its 21st day on Friday, tying it with the longest shutdown to date, and many of the 800,000 employees who have been furloughed or who are working without pay missed their first paychecks.

The White House and congressional Democrats remain divided over Republican President Donald Trump’s demand for money for a border wall, even as the president warned in Texas on Thursday that he may use emergency powers to bypass Congress and get billions of dollars to build it.

The shutdown, which began on Dec. 22, is the 19th since the mid-1970s, although most have been brief. A 1995-1996 shutdown over a funding battle between Democratic President Bill Clinton and Republican House of Representatives Speaker Newt Gingrich also lasted 21 days. The current one has not affected three-quarters of the government, including the Department of Defense and the Postal Service, which have secure funding.

Some 800,000 employees from the departments of Homeland Security and Transportation, among others, have been furloughed or are working without pay. Private contractors working for many government agencies are also without pay and private companies that rely on business from federal workers or other consumers – such as national park visitors – are affected across the country.

The following is what is happening around the federal government:

INTERNAL REVENUE SERVICE

Nearly 70,000 IRS employees, or about 88 percent of the workforce, have been furloughed, raising concerns about American taxpayer filings and refunds and the ability of the agency to manage government revenues ahead of the April 15 income tax filing deadline. [L1N1Z41SL]

The acting director of the White House’s Office of Management and Budget, Russ Vought, has said tax refunds would be distributed despite the shutdown.

HOMELAND SECURITY

The department that oversees Customs and Border Protection, Immigration and Customs Enforcement, the Transportation Security Administration, the Coast Guard and the Secret Service is affected.

Of 245,000 agency employees, nearly 213,000 have been deemed “essential,” according to the department’s contingency plan, so they are working without pay until a funding bill is passed.

More than 50,000 TSA officers are working without pay, but Democratic lawmakers have expressed concern about some transportation employees failing to show up for work or calling in sick. The TSA said on Tuesday the absences were having “minimal impact.”

HOUSING AND URBAN DEVELOPMENT (HUD)

Most of this department’s 7,500 employees are “non-essential” and only about 340 are working. Nearly 1,000 others may be called in for specific tasks, without pay.

The shutdown has left administration officials scrambling to prevent the eviction of thousands of people covered by a HUD program that expired on Jan. 1 and now cannot be renewed, according to the Washington Post.

Public housing authorities and Native American tribal housing entities are not part of the federal government and so are not required to shut down. But the federal government provides some of their funding, so some have reduced services or changed operating hours.

HUD, which oversees some housing loan and low-income housing payment programs, warned in its contingency plan that “a protracted shutdown could see a decline in home sales, reversing the trend toward a strengthening market.”

INTERIOR

The National Park Service, under the umbrella of the Interior Department, is operating with a skeleton staff. Under its contingency plan, some parks may be accessible, with others closed completely. The park service is providing no visitor services such as restrooms, facility and road maintenance and trash collection. Some volunteers have worked to clean up sites, according to media reports, and some states and other localities have also pitched in funding to keep parks operating. Campgrounds have begun closing because of sanitation issues.

The parks are losing about $400,000 a day in fees because no rangers are staffing the entrances, according to Senate appropriators. The park service has authorized using previously collected entrance fees to bring in additional staff to clean up trash and other tasks in a move some critics have said is illegal, the Washington Post reported.

The Smithsonian museums and the National Zoo in Washington, which receive U.S. government funding, are also closed.

COMMERCE DEPARTMENT

The Department of Commerce’s Bureau of Economic Analysis and Census Bureau is not publishing economic data, including figures on gross domestic product, inflation, personal income, spending, trade and new home sales, during the shutdown.

OFFICE OF PERSONNEL MANAGEMENT

The agency that oversees the federal workforce has given advice to workers on dealing with landlords, mortgage lenders and other creditors, including sample letters explaining severe income loss because of the lack of federal funding. Some federal workers are applying for unemployment benefits, according to media reports.

JUDICIARY

The U.S. court system said on Monday it could operate until Jan. 18 and that most proceedings would continue as scheduled. Cases involving furloughed lawyers from the executive branch of government may be delayed. After funds are exhausted, courts may operate as necessary, but it would be up to each court to set staffing, the system said in a statement.

The shutdown over the border wall is also straining the country’s immigration system and has been blamed for worsening backlogs in courts. Immigration judges are among those furloughed, leading to thousands of long-delayed deportation cases being rescheduled.

HEALTH

The Food and Drug Administration and other agencies under the Department of Health and Human Services are partially affected by the shutdown. Some food and drug inspections are on hold, but the FDA says it is still able to respond to emergencies, such as foodborne illness outbreaks. The Indian Health Service is not able to provide most of its funds to tribes and Urban Indian Health programs. Some scientific research projects also cannot continue in full.

AGRICULTURE

The Department of Agriculture said on Tuesday that U.S. farmers could have more time to apply for aid aimed at mitigating any harm during ongoing trade disputes with China, among others, adding that farmers who had already applied would continue to receive payments.

USDA has also delayed several key reports on major domestic and world crops that were due to be released on Friday, Jan. 11. {nL1N1Z40VT]

Funding for food aid for low-income Americans, known as the Supplemental Nutrition Assistance Program or SNAP, will continue in February, Agriculture Secretary Sonny Perdue said on Tuesday, but he warned the outlook for March was uncertain if there was no end to the shutdown.

FEDERAL COMMUNICATIONS COMMISSION

The FCC, which regulates radio and television broadcast and cable systems, has suspended most operations. Work for “the protection of life and property” will continue as will operations at the agency’s Office of Inspector General, the FCC’s internal watchdog.

TRANSPORTATION DEPARTMENT

Of its 55,000 employees, 20,400 have been put on leave. That excludes most of the Federal Aviation Administration, where 24,200 are working and the Federal Highway Administration, where all 2,700 employees are funded through other sources.

Air traffic control, hazardous material safety inspections and accident investigations continue, but some rule-making, inspections and audits have been paused.

The National Highway Traffic Safety Administration (NHTSA) has furloughed nearly 60 percent of its staff, halting auto safety investigations and new vehicle recall notices. The agency said it would recall furloughed employees if it “becomes aware of an imminent threat to the safety of human life.”

Air traffic controllers and other aviation industry workers protested on the Capitol grounds on Thursday. National Air Traffic Controllers Association President Paul Rinaldi warned that the funding impasse would hurt the development of procedures to accommodate “over 1,000 aircraft wanting to go to Atlanta” at the beginning of February for the Super Bowl.

EXECUTIVE OFFICE OF THE PRESIDENT

An estimated 1,100 of the office’s 1,800 employees are on leave. That includes most of the Office of Management and Budget, which helps implement budget and policy goals.

NASA

Most employees at the National Aeronautics and Space Administration are on furlough. The small percentage who remain are working without pay. Work on any satellite mission that has not yet launched will be suspended until the agency receives funding, according to its contingency plan.

ENVIRONMENT

The Environmental Protection Agency has furloughed most of its 14,000 workers, with fewer than 800 deemed “necessary to protect life and property” reporting to work without pay. Workers who monitor pollution and clean up superfund sites are among those furloughed.