A collection of mints can become an unidentified mixture once labels fade and stems spread between pots. Keep each variety in a clearly marked container and inspect the gaps between them.
Use the botanical or cultivar name supplied by a reliable nursery. Names based on scent can be appealing, but personal impressions are not a dependable replacement for a label.
Make a small reference file
Photograph the whole plant, a mature leaf and the flower spike when available. Pair those images with the label and the date. Different growth stages can look unlike the photograph used in a catalogue.
When dividing or taking cuttings, label the new pot before moving material into it. Do not rely on remembering which of several similar-looking shoots came from which parent.
If a name is lost, keep the plant recorded as uncertain while you investigate. Rubbing a leaf and recognising a familiar scent may suggest a possibility without confirming it. For cooking or sharing named plants with someone else, obtain a trustworthy identity rather than passing along a guess that becomes harder to correct later.
The RHS mint guide distinguishes numerous species and cultivated varieties, and cautions that not all are suitable for cooking. A faded label should be resolved through a reliable supplier, not replaced by a guess based only on scent.
Related reading: Mint Varieties: Comparing Leaves, Flowers and Scent.