Instrument descriptor
The human-readable string a depository uses alongside a debt security's ISIN, encoding the issuer name, coupon rate, security name, redemption date and face value in one line.
In plain language
An ISIN uniquely identifies a security, but it is just a code — it tells a DP or investor nothing about the instrument on its own. Debt securities also carry a second, readable identifier: the instrument descriptor.
Where the ISIN is opaque, the descriptor is designed to be decoded at a glance: it packs the issuer's name, the coupon rate, a short security name, the redemption date and the face value into a single line.
How it works
From Chapter 11, section 11.1: the instrument descriptor in the depository system indicates the name of the Issuer, the coupon/interest rate, the security name, the redemption date, and the face value.
The workbook decodes its own worked example: "ICICI BANK LIMITED SR-B98 14.25 UMD 14FB05 FVRS1LAC" reads as Issuer ICICI Bank Limited, coupon 14.25%, instrument Series B98 UMD, redemption date 14/02/2005, face value Rs 1,00,000.
The depository forwards the complete instrument details to all Depository Participants through circulars, so that every DP dealing in that ISIN can independently verify what the descriptor represents. The descriptor also changes at a defined moment: when a secured debenture's Letter of Allotment is converted to a debenture certificate on creation of the charge, the ISIN's descriptor nomenclature is updated from "LOA" to the debenture's own name.
A worked example
A DP receives a debt instrument with the descriptor "KMPL 9.5 LOA 29DC05 FVRS1LAC". Decoding it exactly as the workbook's method works:
| Field | Value |
|---|---|
| Issuer | KMPL |
| Coupon rate | 9.5% |
| Instrument status | LOA (Letter of Allotment) |
| Redemption date | 29/12/2005 |
| Face value | Rs 1,00,000 |
Once the charge on this secured debenture is created, the descriptor changes to "KMPL 9.5 NCD 29DC05 FVRS1LAC LOA UPTO 23MR05" — the nomenclature moves from LOA to NCD, and the descriptor now also records that the LOA stage ran until 23 March 2005. The ISIN itself does not change; only the descriptor's wording is updated to reflect the instrument's new status.
Why NISM asks about it
Chapter 11, section 11.1, introduces the instrument descriptor immediately after ISIN, with a fully worked decoding example. Expect the workbook's own decoding exercise tested directly, and the LOA-to-debenture descriptor change as a follow-up question.
Common exam traps
- The descriptor is not the ISIN — the ISIN is the unique code; the descriptor is the readable label built from the instrument's features.
- The descriptor changes when an LOA converts to a debenture on creation of charge — the ISIN itself stays the same throughout.
- Two instruments with identical features but a different coupon, redemption date, put/call date or interest schedule get separate ISINs and separate descriptors — a debt instrument is never assumed identical to another just because the issuer is the same.
Where this is taught
Free preparation for NISM Series VIRelated terms
- Debt securityA written agreement to repay a loan, usually with interest, within a set time. Bonds, debentures, CP, CDs, G-Secs and T-Bills are all debt securities, and any type can be admitted to the depository.
- ISINThe 12-character code (ISO 6166) that identifies one specific security in the depository system — country prefix, nine-character basic number and a check digit, as in INE475C01012.
- Letter of AllotmentThe provisional instrument a company allots for a secured debenture before the charge over its assets is created — once the charge is created, the same ISIN's descriptor changes from LOA to debenture.