ISDA SIMM 2.9+2606.4: Preparing for the December Update
ISDA SIMM 2.9+2606.4 provides a useful reference for firms preparing for the 5 December 2026 effective date. It is still explicitly a draft, not a confirmed final release, but should be a good reference for what the final release might look like.
For portfolio managers, risk teams and treasury, the practical question is how the update could affect initial margin and collateral needs. Changes to risk weights, correlations and currency classifications can affect portfolios differently, even when their headline exposures look similar. Comparing your own positions ahead of the transition gives you time to understand those differences and plan funding.
As of 19 October 2026, the current effective version remains 2.8+2512, which ISDA made effective on 11 July 2026.
Understanding the Version Numbers
| Version | Role for users |
|---|---|
| 2.8+2512 | Current effective release and the baseline for assessing the change in margin. |
| 2.9+2512 | Earlier reference for assessing the 2.9 methodology using the December 2025 calibration data cut-off. No effective date was assigned to this combination. |
| 2.9+2606.4 | Latest reference for preparing for the December update, incorporating the June 2026 calibration cycle. |
The first part of the name identifies the methodology version. The four digits after + identify the calibration data cut-off, in year/month form. The .4 identifies the revision. These numbers help distinguish the calculation approach from the market-data period used to calibrate it.
ISDA's September 2026 Governance Framework update reiterates its commitment to at least semiannual recalibration. The December and June data cut-offs identify calibration cycles, rather than the months in which users switch models.
Why Are There Two 2.9 Versions?
The two versions help answer different questions. Comparing 2.9+2512 with 2.8+2512 holds the calibration cut-off constant, making it useful for examining the effect of the methodology changes. Comparing 2.9+2606.4 with 2.8+2512 gives a more current view of the combined effect of methodology changes and recalibration ahead of December.
Our earlier 2.9+2512 analysis explored the first comparison. Firms that assessed their portfolios then can now refresh that work to see how their expected margin has evolved. For firms starting their assessment today, the most useful starting point is the latest version against the current effective model.
Preparing for 5 December
The stated effective date is 5 December 2026. Firms can use that date to plan portfolio comparisons, collateral forecasts and operational readiness, with the cutover aligned to ISDA's final implementation guidance and their counterparties' arrangements.
There is value in starting the analysis now. An early comparison can identify which portfolios need closer attention, where changes could affect liquidity buffers, and which differences need discussion with counterparties before the transition.
What Could Change for Your Portfolio?
Interest rates and FX deserve particular attention. Currency classifications and changes across tenors can alter the treatment of an exposure, while correlations affect the amount of offset recognised between positions. A lower headline risk weight does not necessarily mean lower total initial margin.
The latest version also changes parameters across Credit, Equity and Commodity. The direction and size of the impact depend on the mix of sensitivities, the signs of exposures, concentration and diversification. A hedged book can respond differently from an outright position in the same risk class.
For firms that have already analysed 2.9+2512, it is useful to refresh both the calculation and the explanation of its drivers. The latest comparison includes classification changes as well as recalibrated values.
Interactive Comparison: December Update Versus Current Production
The tool below compares 2.9+2606.4 against 2.8+2512, the effective baseline. All charts use the 10-day holding period. Select a risk class, then switch between changes and the two versions' values. The commentary uses the same baseline throughout.
- The inflation risk weight rate is updated to 46 from 51
- The cross-currency basis swap spread risk weight remains unchanged to 21
- The vega risk weight is updated to 0.17 from 0.2
- The historical volatility ratio is updated to 0.8 from 0.74
| 2w | 1m | 3m | 6m | 1y | 2y | 3y | 5y | 10y | 15y | 20y | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2w | -0.02 | -0.01 | -0.01 | -0.02 | -0.01 | -0.01 | -0.02 | 0 | -0.01 | -0.01 | |
| 1m | -0.02 | -0.03 | -0.06 | -0.02 | 0 | +0.01 | +0.02 | +0.02 | +0.01 | +0.01 | |
| 3m | -0.01 | -0.03 | -0.01 | 0 | +0.02 | +0.03 | +0.03 | +0.02 | +0.03 | +0.01 | |
| 6m | -0.01 | -0.06 | -0.01 | -0.01 | +0.01 | +0.02 | +0.02 | 0 | 0 | 0 | |
| 1y | -0.02 | -0.02 | 0 | -0.01 | +0.01 | +0.02 | +0.01 | 0 | -0.01 | -0.01 | |
| 2y | -0.01 | 0 | +0.02 | +0.01 | +0.01 | -0.01 | 0 | -0.02 | -0.03 | -0.03 | |
| 3y | -0.01 | +0.01 | +0.03 | +0.02 | +0.02 | -0.01 | 0 | -0.01 | -0.02 | -0.02 | |
| 5y | -0.02 | +0.02 | +0.03 | +0.02 | +0.01 | 0 | 0 | 0 | -0.01 | -0.01 | |
| 10y | 0 | +0.02 | +0.02 | 0 | 0 | -0.02 | -0.01 | 0 | 0 | 0 | |
| 15y | -0.01 | +0.01 | +0.03 | 0 | -0.01 | -0.03 | -0.02 | -0.01 | 0 | 0 | |
| 20y | -0.01 | +0.01 | +0.01 | 0 | -0.01 | -0.03 | -0.02 | -0.01 | 0 | 0 |
- Between any two sub-curves is updated to 0.972 from 0.981
- Between the inflation rate and any yield is updated to 0.44 from 0.42
- Between the cross-currency basis swap spread and any yield or inflation rate is updated to -0.09 from -0.01
- Between different currencies is updated to 0.3 from 0.35
| Tenor | v2.9+2606.4 | v2.8+2512 | Change |
|---|---|---|---|
| High volatility | 17m | 71m | -54m |
| Regular volatility (well-traded) | 220m | 220m | 0m |
| Regular volatility (less-traded) | 110m | 110m | 0m |
| Low volatility | 370m | 370m | 0m |
These charts describe parameter changes, rather than forecasting the margin change on an individual portfolio. Their colours indicate numerical direction; they do not imply that every portfolio's margin will move the same way.
Turn the Comparison into a Collateral Plan
A useful assessment starts with the same portfolio, sensitivities, calculation currency and holding period under each version. That makes the comparison meaningful and helps separate the model's effect from changes in positions or market conditions.
Focus on three questions:
- Where does margin change most? Review the total and the contribution of each risk class, paying attention to concentrated exposures and offsets.
- What does that mean for liquidity? Assess the potential change in collateral needs across representative portfolios and relevant market scenarios.
- Can you explain the differences? Check currency classifications and sensitivity mappings, and reconcile material differences with counterparties ahead of cutover.
Assess the December Update with Cumulus9
Cumulus9 supports 2.9+2606.4 for portfolio impact assessment at both 1-day and 10-day holding periods. You can compare the latest version with the current effective model to understand the effect on your own exposures and prepare your collateral plan.
As an ISDA SIMM licensed vendor, Cumulus9 helps firms turn model changes into practical margin analysis. Get in touch to discuss a comparison of your portfolios on the Cumulus9 platform ahead of December.
Release status and analysis as of 19 October 2026.