FWIW, I work as a self-employed researcher/writer, mainly - but not exclusively - for one company. Since ALL your businesses, or none, have to be VAT registered, I registered this for VAT when I set up my helicopter pilot business, saying that the writing was my main business. In due course I got a "courtesy call" from my local VAT office. I explained the whole situation quite honestly, asking again if it was OK, and was told it was. I was then asked my turnover, which is way below the VAT threshold. She said: "So why have you registered for VAT; oh, I see, it's becuse you want to claim it back on your helicopter training". I said that was the case, and she seemed to think that was fine. She said I might have a visit "just to check you're coping with the paperwork" but so far the visit hasn't materialised. The company I mainly work for said it probably won't; they'll realise they're not likely to make much out of me right now, and won't bother coming out. I'm relying on being totally open and honest about what I'm doing...and keeping my fingers crossed.