Brake fluid is easy to forget because nothing on the dashboard announces when it has gone old. The fluid draws moisture from the air over time, and the owner's manual sets the interval for replacing it. The service is short, but it touches the part of the car that stops it, so the questions you ask before the work starts matter as much as the steps that follow.
Find the interval and the fluid type
Look in the owner's manual for the brake fluid replacement interval and the fluid type the manufacturer specifies. Then check the cap on the brake fluid reservoir, which usually names the type as well. Use the type on the cap and in the manual. Do not mix fluid types, and do not top off with whatever is on the shelf. Write the interval and the type on the same sheet where you track your other maintenance so the next due date is not a guess.
Decide who does the work
Brake fluid service involves opening the system, draining old fluid, refilling, and bleeding air out at each wheel in a set order. If you do not have the tools, the training, and a clear way to keep air out of the lines, hire the work out. Whoever does it, the job should end with a clean reservoir at the correct level, a firm pedal, and a written record.
Questions to ask the shop before the work starts
Ask which fluid type they will use and whether it matches the cap and the manual. Ask how they bleed the system and in what order they go through the wheels. Ask whether they inspect the brake lines and hoses while the system is open, and whether they will note any leaks or soft spots on the invoice. Ask whether the invoice will list the fluid type, the quantity used, and the odometer reading on the day of service. If the answers are vague, get the shop to write them down before you hand over the keys.
The steps you should see
A proper service checks the reservoir level and the fluid condition, drains the old fluid, refills with the correct type, bleeds each wheel until clean fluid runs through with no air, and then tests the pedal feel before the car leaves. A pedal that feels soft, spongy, or sinks slowly under steady pressure after the work is a reason to stop and return the car to the shop before you drive it farther. Brakes are a safety system, so treat any change in pedal feel as urgent, not as a detail to watch.
Keep the paper
The invoice is your record. Keep it with the car's other service documents and note the date and odometer reading in your own log as well. If a service contract or warranty depends on maintenance records, the invoice that names the fluid type and the work performed is the proof you will want. Read your own contract's maintenance clause to see what it asks you to keep, and keep whatever it names.