When is ambiguous. When is somewhat ambiguous, since it brings two clauses into a somewhat explanatory conjunction with each other, contains elements of conditionality and implies a reference to timing but does none of these things in a very precise manner. The conditionality is somewhat blurred because when may be interpreted as if…, as as long as… and as during periods that… The latter two interpretations do not necessarily contain crystal clear cut-off points as to whether or not a condition is met.
If is a condition. If refers to a clear-cut context of ‘yes’ or ‘no’, ‘true’ or ‘false’. For example, “if the 100,000 boxes are delivered, the addressee shall pay €1 million”. On its own, the sentence means that the delivery is the relevant point in time triggering the payment obligation and indicates that when only 99,999 boxes are delivered, payment has not yet become due.
Best practice. Do not use if and to the extent that: the phrase to the extent that inevitably implies that the condition to which the extent refers must be fulfilled in order for the following consequences to apply. In all cases, drop if and.