Whether you need to pay SDLT or not depends upon the ‘consideration' and the nature of the transfer of equity. Consideration refers to the amount of the property you will take from the previous owner. Consideration includes both equity (the value of the property) and the value of the mortgage.
If the property is a ‘gift' and there is no mortgage, or the property is split equally between two people, there will be no stamp duty to pay. Similarly, if couples are legally separating or transferring equity by court order, there is no need to pay SDLT.
However, in most cases when the property is split unequally, a mortgage is transferred, or the amount being transferred is over the stamp duty threshold, there may be some tax to pay.
Whatever your circumstances, your transfer of equity solicitor will explain any expected fees and payments to help you take the right course of action for your transfer of equity.