IFRS quantitative finance series
IFRS 9 Management Overlays: Quantification Without Double Counting
Overlays can be necessary when models or data do not capture a material reporting-date risk. They become dangerous when used as permanent buffers, unexplained targets or substitutes for fixing known model defects.
Start with an identified gap
Each overlay should name the risk, affected population, reason the core model misses it and evidence available at the reporting date. The bank should distinguish emerging risks, data limitations, model limitations and operational corrections because they require different solutions.
Quantify transparently
Methods may include scenario differentials, stressed parameter shifts, benchmark loss rates or exposure-specific adjustments. The calculation should show how the adjustment relates to the identified shortfall and how overlap with scenarios, staging and other overlays was prevented.
Design an exit
An overlay needs expiry criteria from inception. Release may follow model remediation, data capture, disappearance of the risk or incorporation into scenarios. Backtesting should compare the original rationale with subsequent evidence rather than judging only whether the total allowance was conservative.
Quantitative expression
Implementation controls
- Maintain an overlay inventory with owners and expiry dates.
- Test overlap with macro scenarios and staging.
- Separate model correction from uncertainty allowance.
- Report additions, releases and rationale to governance committees.