Yes, this is separate from the local tax. Most of the important information is known about this value-related property tax, which is applicable already this year.
This online calculator will let you figure out how much you should pay, based on if it's your first, second, third property in Budapest, what size it is, what district it's located in, market value (you can apparently argue that APEH use this value instead of the general district value - this still seems to be somewhat of a grey area as APEH have stated they will value based on 'market value' but seem to be applying a district value for now).
[broken link removed]
Things to enter before clicking 'SZAMOL':
1. Ingatlan fajtája: Enter 'Egylakasos'
2. Hányadik ingatlan?/First, second or third property: For this, choose 'Elso Ingatlan (nem lakott), assuming you just have one property in Hungary and that you don't live here.
3. Ingatlan Helye: Choose the district it's in.
4. Hasznos alapterület/Size
5. Forgalmi érték/Market Value: Enter this if you know it. Alternatively the average district value will be used.
(To come closer to the APEH 'market value' if they use this, first fill in the lower section 'Korrekciós értékek' before copying this amount from the
'Korrigált számított érték' into the 'Forgalmi érték' section and clicking 'SZAMOL').