I purchased a new Apple Watch 9 online and it doesn’t have a IMEI number. Can it still be used for cellular service?

If you do not see the IMEI in Settings > General > About, your Apple Watch is not a cellular model. To double-check, see if you see “Cellular” in Settings.

Which model did you Purchase?

What is the model number?

To have an IMEI number and be able to use cellular, it must be a cellular model. "GPS+Cellular" as labeled in the Apple Store.

GPS only models cannot use cellular service.