Can I do that? Technically, your super fund can buy any type of property as long as it has enough cash, or the purchase is structured to comply with the new borrowing requirements. But there are special concessions within the super rules excluding "business real property" from the related party transactions and in-house asset rules. Put simply, this means that while your fund can't buy other types of property from related parties, such as you, your family or your business, it can purchase a business property. Similarly, the restrictions on in-house assets don't apply to business properties leased to related parties.

These exemptions are most commonly used by small businesses who sell premises to their super fund, then rent them back. The business gets the cash that would otherwise be tied up in the premises, and the super fund gets an income and - hopefully - a growing asset for your retirement.

Does this apply to any business property? Ah, there's the catch. It applies to property "used wholly and exclusively in one or more businesses carried on by any entity". On the plus side, that means the concessions don't just apply to your own business premises. If you, for example, own a high-street shop that's rented to a completely unrelated business, it should still pass the test.

But that "wholly and exclusively" bit can be tricky.

It means that if the property has a mixed use - maybe that the shop has a flat on top - it generally won't be eligible for the concessions.

The question of what qualifies as business real property has often proved contentious, so last week the Tax Office issued a draft ruling, SMSFR 2008/D3, to try to clarify the issue.

Bear in mind that this is still a draft ruling on which the Tax Office is seeking comment, but it gives a helpful insight into the regulator's thinking.

Hopefully the ruling will be finalised later this year.

So what does it say about that shop with a flat on top? It would be unlikely to pass the business test. As a general rule, the Tax Office regards residential use of a property as not falling within that "wholly and exclusively" definition. But there are exceptions. The draft, for example, allows that a motel which includes a manager's unit should fall within the definition as the use of the unit is incidental and relevant (another important definition) to the business.

The draft also canvasses the case of a shop with a flat on top that is empty and has become uninhabitable. The owner is considering renovating it to extend her hairdressing salon. In this case, the draft says, the non-business use has permanently ceased and, while the whole of the premises is not used by the business, it is used to an appreciable degree and should qualify as business real property. There is also a special exemption for residential dwellings on primary-production businesses. As long as the area used for private purposes does not exceed two hectares, and is not the predominant use of the property, the "wholly and exclusively" test is met. In other cases, it's a question of determining whether the activities being undertaken qualify as a business.

The Tax Office gives the example of two bed and breakfasts. In one case, three bedrooms are set aside for paying guests during school holidays, but the family uses the remaining rooms. The Tax Office says the scale of this operation is not sufficient to be considered a business. But a home used predominantly as a B&B year-round, for which the proprietor advertises the business, employs staff, has a business plan and pays tax could qualify.

The draft also allows that, in some instances, investing in property may qualify as operating a business. But it will depend on the scale of the operation and how it is managed.

The draft ruling covers a daunting 68 pages and shows just why investors can find the rules on business real property confusing. But if you're looking at selling a business property to your super fund - or renting business property from it - it's a must-read.