Revenue has insisted it is not penalising people selling homes for a higher price than their declared property tax value.
It follows reports today that hundreds of people have had to pay extra tax before they can close a sale on their homes.
Officials say that if a property sells for 15% over the top of the tax band that its value falls into, it has to go through a written clearance process.
It raised concerns that more people could be caught out in the market where some areas are seeing rapidly rising house prices.
However Revenue spokeswoman Ann Looney said Revenue just wanted to make sure homeowners were upfront in the first place.
"We are not about to penalise people for any increase in (house) value since they originally declared, but we do want to clarify that the original declaration of value was correct," she said.