The best way to deal with potential Conflicts of Interest is to openly declare these. Just because you have a relationship with someone doesn't mean this is going to be an issue or lead to fraud, but it is a good idea to keep a written record of these.
It wouldn't be a risk register, because how can you rate someone's risk of doing something dodgy? Risk registers are for objective risks such as Health and Safety.

The lowest risk to the buyer is 'delivered duty paid'. This is because the supplier does all the work transporting the items to the buyer's premises. Incoterms_2020_chart | Intersped

Under EU Public Procurement rules, the permissible procurement procedures include the Open Procedure and the Restricted Procedure. The Open Procedure allows any interested party to submit a tender, while the Restricted Procedure involves a two-stage process where only selected candidates are invited to submit tenders. These procedures are designed to ensure transparency, competition, and equal treatment in public procurement.
Exact Extract from Study Guide:
"The EU Public Procurement Directive outlines several procedures including Open Procedure and Restricted Procedure, which are designed to facilitate fair and transparent procurement processes."

A credit rating generates a score which reflects 'the level of risk an organisation poses when dealing with other businesses'. It's saying how risky it is to loan them money or do business with them by looking at how good they are at paying people. So a high credit rating will say they're good at paying back their loans and paying their suppliers on time. A poor credit rating will say they often miss payments or pay late.
A credit rating will not tell you how much money they have, or details on their prices. Credit scores looks at purely financial data so wouldn't help you analyse whether their business practices are ethical or not.

Advertising tenders is crucial for achieving value for money by encouraging competitive bids, which can lead to better pricing and service offerings. It also provides insights into the market by revealing the capabilities and innovations of various suppliers, aiding in informed decision-making.
Exact Extract from Study Guide:
"Inviting suppliers to take part in a competitive tender may reduce the potential for the biased selection of a supplier. Time, money and resource could be saved..."