Can someone tell me how the radio serial number looks like? For example, how many digits altogther? Does it contain number/alphas combination or just plain numbers?

I think the S/N and code are written in the maintenance manual but not 100% sure.

Would appreciate if someone give me a hint.

Thanks.

The radio code for a 1999 A4 is as follows with L representing a letter and N representing a number:
LLLNLNLNNNNNNN
The code is a four figure number.

Tom C

Sorry Samantha, the long sequence of letters and numbers is the serial number and the short sequence the code.
Tom C

This reminds me. My conert radio manual does not have a serial number or code on it. What should I
do?

ROB L

For what it's worth, Rob, I had a used BMW with no radio serial number and code. I needed the code for obvious reasons so phoned the local BMW dealer and gave my VIN. Surprisingly they got back to me a few hours later with the code. Try this approach with your local Audi dealer, it could be successful.
Tom C