So just bought a tag, stuffed it in the seat tube.

I then go to register.
I create an account and then register my tag.

It asks for bike details etc, but nowhere does it ask for my immobi tag number.

So how do they tie the bike to me?

what does

register my tag

involve ?

Have you actually followed all the steps?

https://www.immobilise.com/help/registerimmobitag

Well I did do that and with not seeing anything obvious I added the immobi tag number under identifiers along with frame number.

I was expecting a more obvious box saying enter immobi tag number here.

As far as DB relational searches go I’d have thought that’d be a lot easier.

Looks to me like step 5 is exactly that, enter your tag number??