If someone says “I am a Companion,” the claim is first tested against historical possibility. A claim made in a chronology that rules out an encounter with the Prophet ﷺ cannot establish Companion status.
Even when the encounter was chronologically possible, a self-report is not automatically conclusive in all circumstances. The credibility and uprightness of the person making the assertion raise a further evidentiary issue, which hadith scholars explicitly recognized.
A sound investigation compares the alleged person’s dates, known locations, circumstances during the Prophetic lifetime, and independent transmission evidence before accepting an attribution.