I've just found that the council tax discount and exemption system in Scotland is slightly different from that in England (and Wales?). That's not of immediate practical significance to practitioners in England and Wales but it does offer some interesting precedents.

If you are interested in reading more about the Scottish system, there is a link to the relevant web-page here.

The main differences are:

1. On long-term empties, local authorities have discretion as to the level of discount but subject to a minimum discount of  10%, (i.e. the same as for second homes).  The reason given is to give greater incentives to owners to report their empties to the council.  The nil discount (100% council tax) option for long-term empties is not available.
2. Although the normal exemption "C" for unfurnished empties applies, after 6 months and up to a year, a mandatory 50% discount applies.  In otherr words, the flexibility offered by (1) only kicks in after a year.  Presumably the council tax system therefore distinguishes automatically and easily homes that have been empty for over a year.
3. Where discounts on long-term empties are raised above 50%, local authorities keep the revenue, the same as for second homes. 

We have argued in the past that (3) should be implemented in  England, with the proviso that it should be subject to a proper empty homes initiative being in place (otherwise LAs have an incentive to keep homes empty rather than the reverse).  In some ways that would fit quite well with the New Homes Bonus, because the NHB would compensate for council tax lost through bringing an empty home back into use.