How do you reset service indicator in Audi A4?

well it depends on what age the car is but generally the following steps should work

• Turn off the ignition
• Press and hold the button on the left side of the display while turning the ignition on
• Service OIL will be displayed
• Pull out the button on the right side of the display until the service prompt is cleared
• The display should now read ---

If the above procedure does not work, outlined below is an alternative procedure:

• With the ignition off, push the right button
• Turn the ignition on and then pull the left button
• This should clear the warning message

Although these 2 techniques i found didnt work on my dads 1999 Audi a4 1.9tdi so i had the ignition turned off then held down both buttons on the display and turned the ignition on and that reset my dads service clock.