GOV.UK
Examinations: Information: Post-award examinations: Conditions
S16 is more restrictive than S14, as it requires you to believe the award is incorrect before you issue a formal information notice. In practice this will make little difference, as all the cases you examine in-year will have been identified on the basis of risk.
In other words, you will have grounds for believing the award may be incorrect in every case. But you are not obliged to give reasons for examining the claim and you should not do so in any case.
You should note that S16 only allows you to examine the claim during the period for which the award of a tax credit is made, i.e. from 6th April (or later if the claim is made later in the year) to 5 April the following year.