What should you use when communicating with your bidder?
When a supplier (bidder) raises a Clarification they just see a Number (eg 43) in their CQ list (see image below). They will not understand the Authority reference to the CQ eg CL-001.
The reason for this is: as each CQ is generated, regardless of supplier, it is given a CQ reference, these are sequential to enable the Authority to easily track them. If the supplier could see this reference it is possible for them to guess (infer) there are other suppliers in the competition etc.
For example, if the supplier sends a Clarification and could see it as reference CL-001, they then send another Clarification and see it as reference CL-007, they can infer 5 other questions from other suppliers have been sent to the authority. So, by just giving the supplier a number for a Clarification, all the supplier can see is how many Clarifications they have raised.
However, adding to this, since all bidders can see the Clarification Notices, these just use (need) the reference (nothing to infer).
If the Authority is speaking direct to a single supplier re their Clarification - use the number
If the Authority is speaking to all suppliers re a Clarification Notification - use the CN-reference
If the Authority is speaking internally to the PT re any communication - use the reference