Start with an observation
“Twelve accounts used two device references” describes an observation. “One person owns all twelve accounts” is an inference. Keeping the two separate makes a review easier to challenge and improves the handoff to the next analyst.
Keep an alternative alive
A shared network can reflect a household, office or residence. Repeated attempts can reflect automation or a faulty integration. List plausible alternatives, then ask which additional evidence would make one explanation fit better than the others. Do not collect more data simply because it exists.
Match the action to the evidence
An investigation lead may justify a review without justifying a final finding. Consider the actual policy, immediate exposure, customer impact and whether an action can be reversed. A temporary control still needs an owner, a review time and release conditions.
Leave a decision someone can revisit
A useful note separates the observed pattern, your interpretation, the unresolved question and the next action. “Suspicious customer” is not enough. “Hold the disputed credit under the stated terms while eligibility is checked by Friday” can be reviewed and challenged.