Double council tax for 15,000 empty homes
More than 15,000 empty homes were charged double council tax last year in a bid to reduce the number of unoccupied properties in Scotland.
BBC research found councils such as Aberdeen, Edinburgh and Fife had raised millions in extra revenue while others had not used the powers at all.
Glasgow City Council has just begun to use the levy which has been available to local authorities for four years.
Campaigners said the premium had a part to play in getting homes back into use.
How does it work?
Since April 2014, Scotland's local authorities have been allowed to charge 200% council tax on properties that have been unoccupied for more than a year.
The aim of the law change was to reduce the estimated 37,000 homes lying empty across the country.
The discretionary charge was intended to encourage owners to bring empty properties back into use and reduce the blight of unoccupied homes.
It does not apply to second or holiday homes, where the owner can prove they are used for more than 25 days a year.
How much has been raised?
Freedom of Information requests to all 32 Scottish local authorities showed that almost £36m of additional revenue has been raised in the past four years - about £12m last year.
Aberdeen City Council claimed the most additional revenue under the new policy, almost £2.4m in 2017.
Perth and Kinross drew in £1.48m, Edinburgh gained an additional £1.14m and Fife raised the same amount.
Who does not use the power?
Scotland's largest council, Glasgow, told BBC Scotland it had begun to use the empty property powers in April this year, four years after they became available.
It said: "The premium exists to try to discourage owners from leaving properties vacant, which can have a detrimental impact on communities and encourage anti-social behaviour."
The council has no figures for how many times it has used it so far.
South Ayrshire and West Lothian have also just started to use the powers.
East Ayrshire, East Renfrewshire, East Dunbartonshire, South Lanarkshire, Orkney and Shetland do not currently charge extra council tax on long-term empty properties.
What does each council do?
Aberdeen - 1,063 empty houses charged double last year - £2.37m raised
Aberdeenshire - 677 empty houses charged last year - £520,642 raised
Angus - 286 empty houses charged last year - £270,165 raised
Argyll and Bute - 744 houses charged last year - £552,789 raised
Clackmannanshire - 76 houses last year - £45,000 raised
Dumfries and Galloway - 1,748 houses last year - £457,462 raised
Dundee - 275 houses last year - £279,888 raised
East Ayrshire - starting policy next month
East Dunbartonshire - starting April 2019
East Lothian - 256 empty houses charged last year - £78,590 raised
East Renfrewshire - No policy
Edinburgh - 1,181 empty houses charged last year - £1.14m raised
Falkirk - 381 houses last year - £377,974 raised
Fife - 1,741 empty houses charged last year - £1.14m raised
Glasgow - Started charging in April 2018
Highland - 744 empty houses charged last year - £764,249 raised
Inverclyde - 731 empty houses charged last year - £122,000 raised
Midlothian - 249 charged last year (the first year it charged) - £127,567 raised
Moray - 339 houses last year - £298,715 raised
North Ayrshire - 465 houses charged last year - £279,930 raised
North Lanarkshire - 867 houses last year - £283,412 raised
Orkney - No policy
Perth and Kinross - 843 empty houses charged last year - £1.48m raised
Renfrewshire - 378 houses last year - £299,000 raised
Scottish Borders - 1,316 houses charged last year - £611,881 raised
Shetland - no policy
South Ayrshire - Started from April 2018
South Lanarkshire - no policy
Stirling - 319 houses last year - £282,781 raised
West Dunbartonshire - 65 houses charged last year - £23,031 raised
West Lothian - started from April 2018
Western Isles - 336 houses last year - £174,488 raised
Paying full whack
Maureen Dixon's house in Arbroath has been empty for almost four years.
She said: "For a couple of months we didn't have to pay anything, but now we have to pay the full whack.
"Here, we're on band B, which was £114 a month, but we're now having to pay £228."
She and her husband Jim are now renovating it for sale.
The BBC data showed there were 286 properties in Angus which could have double council tax levied on them in 2017.
The local authority's Empty Homes Officer, Sean Maxwell said the policy had already paid dividends.
"Not only does it improve housing demand, it also has positive impacts on the local community," he said.
"Obviously within Angus, we don't want to see unoccupied properties, we'd rather see these brought back into residential use and ultimately local families and local individuals staying in these houses."
Angus Council has operated the policy of charging 200% council tax on long-term empty properties since 2015, and has so far claimed more than £866,000 through the levy.
Why have some councils delayed?
East Ayrshire Council will introduce the empty homes levy in October.
Depute leader Elena Whitham said it had been important to get support mechanisms in place to offer help to owners faced with the threat of double council tax.
She said: "We've now created a full team to support this endeavour so we've got an empty homes officer, we've got teams to help people with restoration and a team to help seek funding.
"I think it really would have been counter-productive had we employed these measures before we had a team like this in place to make sure we can support owners."
She said bringing buildings back into use worked for everyone - providing extra income for the local authority, and improving the environment for neighbours.
The leader of Orkney Islands Council said it was time to reconsider the policy.
Councillor James Stockan told BBC Radio Orkney that in the past the authority decided relatively low numbers of empty homes in their area meant it was not worth the effort of collecting the levy.
He said: "It's really good the BBC has done this piece of work because it has made us aware of where everybody else is now, and I think there is a real opportunity in the next year or two to reconsider this."
Shaheena Din, national manager for the Scottish Empty Homes Partnership, said the empty homes levy could bring revenues which would fund service to help owners get properties back into use.
She said: "On its own empty homes work won't fix out broken housing system.
"But it does have a part to play and it also contributes to a wide range of other council policy areas including safer communities and stronger local economies."