Training for the self-employed

Hi there, I'm helping out a friend and I wanted to get some advice please to make sure I have things clear. She is self-employed, and she will be going on some training which she is funding herself. It is relevant to her business, and she tells me it's a mixture of updating current skills and learning new skills. My understanding is that this means it cannot be claimed as an expense, because the new skills are effectively an asset. Is this correct? If she went on training that is solely updating her current skills, can this be claimed? My research indicated something about "capital allowance", which I'm not familiar with. Is this how it would be claimed, and if so, could anyone give me a link to a resource which explains how this would be recorded in the books? Many thanks Rob