Google can’t find the address?
Are you sure you want to deal with a client with no address?

I would need a company name and address in order to invoice them, for tax purposes if nothing else.

I invoice companies all the time w/o an address. My accountant has never made an issue about it.

It's a bit of a red flag, but not an insurmountable one. If they don't pay you, it's a lot easier to find them if they have an address.

When you are contacted by a national/global firm with many locations, it can be confusing.

Do you not list the client's mailing address on letters, reports, plans, etc.?

Email signatures today are horrible, I frequently struggle to identify senders based on a first name and vaguely familiar corporate domain. OTOH, I also frequently wonder why some folks email to confirm the shipping address in my signature or ask if they can call despite both the desk and cell numbers being given.

I dont share technical details or otherwise without confirming the requestor's physical location and applicable regulation. Not only can their location affect billing/taxes and environmental/safety/other project details, but also who I can/cannot legally talk to. Stateside govt has deemed many aspects of local infrastructure including privately owned plants and commercial products as protected IP that cant be shared with foreign entities/staff, even if those foreign entities own the local infrastructure.

I always require an address for my client's business and the project owner. I won't start a project without it. I include both addresses in all my agreements. If they give me some BS that they can't provide it, I tell them it is required for permitting purposes and I won't proceed without it.

On the flip side, I never give out my physical address. I have a PO box for my business, and if any entity requires a physical address, I give them my registered agent's address (my RA allows this).