“In our view, a deliberate inaccuracy occurs when a taxpayer knowingly provides HMRC with a document that contains an error with the intention that HMRC should rely upon it as an accurate document. This is a subjective test. The question is not whether a reasonable taxpayer might have made the same error or even whether this taxpayer failed to take all reasonable steps to ensure that the return was accurate. It is a question of the knowledge and intention of the particular taxpayer at the time.”