Fortunately in the UK (and many other countries), everything is already subtracted (which can confuse people when they start out and think they can subtract them!)

The way to know for sure is to do the math:-

kCal = 4 * Protein + 9 * Fat + 4 * Carb

/me picks up pork scratchings, although not the best example:-

578 = 4 * 52 + 9 * 41 + 4 * "Trace"

So I can see from this that "Trace" is approx 1g carbs per 100g, but this is probably smaller due to rounding on the other two.

If 4 * protein + 9 * fat + 4 * carb isn't the same as kCal, then fiber hasn't been subtracted.