Good evening! This week's edition of the In Common newsletter comes from Robin McAlpine.

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The council tax is a bad tax and everyone knows it.

We have the power to change it in Scotland and doing so isn't particularly complicated (depending on the replacement). Literally the only things keeping it alive are political cowardice and a lack of agreement on what to replace it with. Let me explain how Common Weal arrived at our proposal – a property tax which taxes any property held in land and buildings.

We set five key criteria for a local tax: It must increase democratic accountability, it must be fair, it must be easy to understand, it must be easy to calculate and collect and it must also contribute to a balanced tax base. The proposals for council tax replacement fall into three categories – tax property, tax land or tax income. How do they stand up against these tests?

Income tax is widely perceived as fair and so many readers will incline towards some form of local income tax. Income taxes are also easily understood, but implementing one locally creates collection difficulties. The existing tax system taxes people where they work so assigning tax to the right local authority can be tricky.

READ MORE: ​Lack of local tax reform 'one of Holyrood's biggest failures'

This also makes it difficult to be properly locally democratic – if local authorities are each able to set their own tax rate the whole system becomes really complicated, but then if it is a flat rate tax Holyrood would be as well abolishing council tax, raising the equivalent through income tax rises and then just passing the money on.

But this highlights the real issue – income is already taxed. In fact income is already taxed twice, through income tax and National Insurance. Yet income tax only taxes you on your annual earnings, not on all the wealth some have accrued already (often by avoiding income tax in various ways). Loading all personal taxation onto income tax is a bad idea, for example because it exempts wealthy retired households from contributing to services.

You can't have a local wealth tax (which would be mind-numbingly difficult to create and run), and yet there is a really very good proxy for wealth already available – housing. The vast, vast majority of Scotland's wealth is held in property and pensions. If you want to tax wealth, tax property.

Taking tax off wealth and putting it onto income is going the wrong direction. So what about a land tax of some sort? That is also a proxy for wealth (and housing) and has a range of valuable policy impacts precisely because it expands the tax base. It is a holy grail for many land reformers.

Common Weal wholeheartedly agrees – but there is more than one way to tax land. Most land taxes are formula-based, assigning a notional land value to all land (farmland being worth much less than the land under prime city centre real estate) and multiplying this by the amount of land owned. So three of the five criteria are comfortably met because it is fair, broadens the tax base and can be set locally.

But it is not easy to understand. Let's say you're renting the middle flat of a four-story tenement in Dundee. What would you make of a letter setting out the tax amount on the land you own? It isn't intuitive.

And the more fundamental problem is that it is really complex to administer. First you have to allocate a value to every square metre of land in Scotland. Then you need to work out the precise square meterage of every single property. That is time intensive and creates endless anomalies at every boundary. (Some house is going to be on the other side of a boundary to its neighbour, and so will get a different tax bill on an identical house.)

All of this is done purely to identify a meaningful value of land so that it can be taxed. But there is another way to identify the meaningful value of land, or at least for the vast majority of people there is. Because for anyone who owns only the land their house is on (in Scotland that's virtually all of us), the value of their land and the value of their house are the same thing.

(Image: File)

Just value the house and you're there – land and building valued. And you can do that with a computer algorithm based on the value of sales of similar houses in the area. It really couldn't be simpler – land-with-housing "values itself" and does so reliably and on an annual basis with no work.

That leaves manually valuing land without residential properties on it which, because of Scotland's concentrated land ownership, isn't all that tricky because there are many fewer properties than you might imagine. Do all this and what you have is a property tax, a single tax which taxes both housing and land on an entirely fair and transparent basis and in a way that is super-easy to calculate and collect.

To replace the current income from council tax like-for-like with our property tax would mean being taxed annually on 0.63% of the value of your property. Over 80% of the population would either be better off or at least no worse off.

A property tax is fair. It is really easy to understand. It is very easy to calculate and collect. It is all but impossible to avoid. It broadens the tax base, includes land and gives you a tax lever you can use to manage house and land prices. It is easily variable at a local level. It is very efficient at raising tax. It is the best solution.

READ MORE: Watch our live council tax discussion with Common Weal's Craig Dalzell

There is a "castle" for sale in Scotland right now. It comprises 10 reception rooms, 13 bedrooms, seven bathrooms, a gym, a billiard room, a cinema, wine cellars, stables, a helicopter pad and its own parkland. It costs £8 million but the owner will only pay £3000 a year in council tax. That is 0.036% of its value or about 20 times less than its fair share of local tax under a property tax system.

The cheapest house I can find for sale in Scotland is a tiny flat in Irvine for £60,000, eligible for a council tax of about £850 or 1.4% of its value. Whoever buys that little flat will pay 40 times more for public services proportionately than whoever buys the castle. In the face of this evidence "too difficult, we don't want to put the effort in" is not an appropriate response. A property tax is.