WASHINGTON – If President Trump and Congress can’t reach a deal to fund the federal government by midnight Friday, it will shut down the government.

That’s happened several times in recent memory, though it’s never occurred when the same political party controls the House of Representatives, Senate and White House.

A shutdown would look a little different than past instances because Congress has already funded about 75% of the federal government.

Here’s a quick rundown of what would happen to some of the more visible federal functions during a shutdown:

Post office: Post offices stay open, and mail delivery continues.

Social Security: Checks for existing benefits will be issued, but processing new applications may be delayed.

National parks: Facilities that require staffing would close but visitors could still access some memorials and open-air parks where staffing isn’t required.

Federal courts: Federal courts usually have enough money on hand from court filings and other fees to stay open for several weeks during shutdowns. After that, they curtail services. Federal prisons stay open.

Border patrols and Homeland Security: 54,000 border patrol employees and 53,000 Immigration and Customs Enforcement employees would continue working through a shutdown, though with their pay delayed.

Passports: Passport processing is suspended during shutdowns, but there may be some exceptions for emergencies.

Travel: Air traffic controllers, luggage screeners and customs agents remain on the job as their work is deemed vital for national security.

National Weather Service: Weather forecasting is a safety issue, so it would stay open.

Veterans: Veterans administration hospitals stay open and benefit checks are issued, but new benefit applications and pending claims aren’t processed.

Active duty military: During shutdowns, military personnel continue to work, but they don’t get paid until Congress provides funding. Some civilian military employees are furloughed.

Smithsonian: Closed.

About 420,000 federal employees who are deemed “essential” would continue to work through a shutdown, ensuring that critical operations in government would proceed unhindered. But these workers would not receive any compensation until the shutdown ends and lawmakers pass legislation to pay them retroactively.