Dell mouse warranty?

There's no on-line method to check warranty the way there is with a computer with Service Tag. Mice and peripherals generally have a one-year warranty.

One of the Community Managers here, DELL-Nathalia M, posted this:

How to get support for your Dell Keyboard and Mouse that is still under warranty

For Mouse/Keyboard bought with a Dell computer:

1. Click Get Help Now on the bottom right corner of this page.
2. Provide your email when requested.
3. Next, provide the Service Tag of the computer with which you bought the keyboard and/or mouse.
4. Briefly explain the issue with your mouse or keyboard.
5. Wait for an agent to be assiged to you. 

For an accessory bought separately or from a non-Dell retailer:

1. Click Get Help Now on the bottom right corner of this page.
2. Enter your email when requested.
3. Next, provide the Order Number (found on the invoice for the keyboard or mouse).
4. Attach a copy of the invoice (image or PDF) to validate the purchase information.
5. Briefly explain the issue with your mouse or keyboard.
6. Wait for an agent to be assigned to you. 

Note: Initially, you will be triaged by our Virtual Assistant (VA) or BOT. Shortly after, an agent will be assigned to your case to provide further assistance.