IHTM14592 - Lifetime transfers: the charge to tax: the charge on lifetime transfers: liability for payment of tax
You can find full details about who is liable for Inheritance Tax on lifetime transfers separately at IHTM30011 onwards.
In general terms, the transferor is liable for tax on an immediately chargeable transfer (IHTM14531), and the transferee is liable for tax on Potentially Exempt Transfers (PETs) (IHTM04057) or additional charges (IHTM14571).