HMRC will tell you whether in their opinion you are caught by IR35. However, it is important to understand that they are not a neutral advisor, and just because someone at HMRC thinks you are caught, that does not mean the actual decision-making process if they challenge your status will lead to the same conclusion. In reality, they have a record of chasing not very many people under IR35 in the first place and then winning only a fraction of those cases when someone has put up a fight.
To be clear, I'm not arguing that this is necessarily due to any ill intent on their part. It's just that even if HMRC people are trying to help when you call them, they can still fail to understand what the tax rules actually say and they can give incorrect advice as a result. When that happens, they seem to err on the side of saying you're caught by whatever it is you're asking about and should pay the extra tax.
If I'd taken them at their word the last couple of times I called, my companies would have paid far more tax than we really owed. (To be clear again, I'm not talking about any funny tax avoidance measures here, just applying the normal but somewhat complicated rules for things like international sales.) Fortunately, we also spoke with some accountants who could explain why the first advice was wrong, which in fact they did by citing parts of HMRC's own written guidance that HMRC's own people had overlooked.
To be clear, I'm not arguing that this is necessarily due to any ill intent on their part. It's just that even if HMRC people are trying to help when you call them, they can still fail to understand what the tax rules actually say and they can give incorrect advice as a result. When that happens, they seem to err on the side of saying you're caught by whatever it is you're asking about and should pay the extra tax.
If I'd taken them at their word the last couple of times I called, my companies would have paid far more tax than we really owed. (To be clear again, I'm not talking about any funny tax avoidance measures here, just applying the normal but somewhat complicated rules for things like international sales.) Fortunately, we also spoke with some accountants who could explain why the first advice was wrong, which in fact they did by citing parts of HMRC's own written guidance that HMRC's own people had overlooked.