I'm self-employed and run a business. From what I've read online, it seems that all income from different business streams is considered when calculating whether I need to register for VAT. However, I'm unclear about whether income from a UK investment counts toward this threshold. The investment income is taxed at source and is included on my self-assessment tax return. I assumed it would be treated separately and excluded from VAT calculations, but now I'm unsure. 

Arthur replies: 

Only your VAT-taxable turnover counts towards the £90,000 registration threshold. That figure is the total value of everything you supply that is subject to UK VAT (including zero-rated items). Income that is exempt (e.g., most financial services) or outside the scope of VAT is left out of the calculation. Typical UK investment returns — bank interest, dividends, coupon income on gilts, most share-deal proceeds — are treated by HMRC as exempt or outside-scope financial supplies, so they do not push you over the threshold. You do still report that investment income on your self-assessment return for income-tax purposes, but it is irrelevant for VAT registration unless the investment itself involves making taxable supplies (e.g., opting to tax a commercial property and charging VAT on the rent).