The normal rule is that if you buy more than one property the extra 3% SDLT is payable.
However, if you buy a property that contains subsidiary dwellings and the main property will be your home you might not have to pay the extra 3%, the rules are in SDLTM07955
SDLT – higher rates for additional dwellings: What is a dwelling – further information
It will be important in some cases to determine whether a premises consists of one or more than one dwelling.
It is a question of fact whether a purchase consists of one or more than one dwelling. A self-contained part of a building will be a separate dwelling if the residents of that part can live independently of the residents of the rest of the building including independent access and domestic facilities.
In certain cases a purchase of more than one dwelling will be treated the same as if a single dwelling had been purchased. This is the case if any of the dwellings purchased are subsidiary dwellings. A subsidiary dwelling must be within the same building as or in the grounds of another dwelling purchased in the same transaction (the principal dwelling). The principal dwelling and the garden and grounds attributable to that principal dwelling must be at least two thirds of the value of the land purchased in the transaction.
There can be more than one subsidiary dwelling purchased at the same time as a principal dwelling, but the principal dwelling must always be at least two thirds of the transaction value.
Where a principal dwelling is purchased and all the other dwellings purchased are subsidiary dwellings, the tests for whether the transaction is a higher rates transaction are applied as if there was only one dwelling purchased. If the purchase of a principal dwelling is a first property purchase or a replacement of a main residence the higher rates will not apply.
Multiple dwellings relief may be claimed where there are separate dwellings.
You can also use Multiple Dwellings Relief with the Subsidiary Dwellings Rules, MDR means you divide the property price by the number of dwellings equally then apply SDLT subject to a minimum of 1% SDLT.
SDLT relief for multiple dwellings
You can claim relief when you buy more than one dwelling where a transaction or a number of linked transactions include freehold or leasehold interests in more than one dwelling.
If you claim relief, to work out the rate of tax HMRC charge:
divide the total amount paid for the properties by the number of dwellings
work out the tax due on this figure
multiply this amount of tax by the number of dwellings
The minimum rate of tax under the relief is 1% of the amount paid for the dwellings.