Hi,
Just to add on, sometimes there is only one parent company that is RADAC registered, then the ID companies spawn brother sister companies to save themselves from registering for GST.
But ultimately the one registering with HDB reno permit will be using the parent ID, where the brother sister companies will be the sub-contracter of your renovation. This is based on my understanding...
I'm talking to a few ID and that's what they say.
Believe it or not, still up to us, but we have to work with someone, so I think rapport is important with any ID.
Cheers