Stamp Duty on a let to buy?

[082612]

I'm looking to convert my current residential to a buy to let and raise funds for the deposit on an onwards purchase and I'm a bit confused in regard to stamp duty? Do I pay the additional rate on my onwards purchase only or do I pay it on the onwards purchase and then also pay a surcharge for converting my current property to BTL as well?

[PallasAthena]

I am assuming you and the properties are in England (different rules in other parts of UK).

Stamp duty (correctly SDLT = Stamp Duty Land Tax) is always payable by the buyer of a property, not the seller, on a transfer of ownership. What you are intending for your current home doesn't seem to involve any sale or transfer of ownership of the property anyway. So ceasing to live at the property and instead using it as a BTL does not involve you in any SDLT liability. It's a change of use.

The change of use may have other financial consequences (eg council tax) and the change of use might need planning permission or other council approval but none of those have anything to do with SDLT.

If you buy another property to live in you will have to pay SDLT on the purchase price (as long it is over the threshold for SDLT). It's irrelevant for SDLT how you raised the deposit money.