We sold a house recently for €300K more than its property tax value, without any issues, or without having to make any back payments or penalties.
Back in 2013, the band it was put into was on the lower side of reasonable.
The sale contract stated the property had been returned in Band X for the years 2013 to 2017, as the purchase price is not more than 80% higher than the upper limit of the band declared, General Condition 4.2.2 shall apply and no further documentation will be furnished.
This was acceptable to the buyer's solicitor.
From the above it would seem, at the moment anyway, if you are over by 80% or less, regardless of the amount, you should be OK.
I have no idea what General Condition 4.2.2 is or where you would find it.