Tax on immovable property

If the said Architect is not registered under GST then He can't issue Tax Invoice.
Only He can give normal bill (Bill of Supply as per GST act)

He cannot charge GST as not registered. Neither you are liable under RCM.

Bill of supply needs to be issued by a registered person when supplying exempted supplies or registered under composition scheme. I dont think so it is for unregistered person..

RCM not applicable.

Also read the word of "NORMAL BILL"

Agree with the above mentioned comments.

If the Architect is not Registered under GST Regime, then he cannot issue a Tax Invoice and collect GST from the recipient.

By virtue of Section 32(1) of the CGST Act 2017, "A person who is not a registered person shall not collect in respect of any supply of goods or services or both any amount by way of tax under this Act."

Hence, the Architect can issue a Bill of Supply/ Normal Invoice.

Regards.