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# NAB reveals a NIM 26 basis points below CBA
- URL: https://www.benchmarkanalytics.com.au/nab-reveals-a-nim-26-basis-points-below-cba/
- Published: 2026-08-17T01:29:57.000Z
- Updated: 2026-08-22T14:01:52.000Z
- Author: Nick Hossack
- Tags: Bank Profits, #banking

NAB's latest trading update highlights one of the clearest differences in profitability between Australia's major banks: its net interest margin is materially below CBA's.

Net interest margin (NIM) measures the difference between the interest a bank earns on loans and other interest-earning assets and the interest it pays to fund those assets, expressed relative to average interest-earning assets. It is one of the most important measures of the profitability of a traditional banking franchise.

Small differences matter enormously because the margin is earned across hundreds of billions of dollars of assets. A 26 basis point difference is equivalent to **$2.6 million of additional annual net interest income for every $1 billion of interest-earning assets**, before allowing for differences in funding mix, asset composition or other factors.

CBA reported a NIM of **2.05%** for FY26\. NAB has now reported a NIM of **1.79%** for the June quarter — a gap of **26 basis points**.

Relevant to note is that NAB's reporting period is different from CBA's full-year result, so the comparison should not be treated as perfectly like-for-like. Nevertheless, the difference in margins is significant.

NAB's headline NIM fell 2 basis points compared with the quarterly average for the March 2026 half year. However, NAB said that excluding Markets & Treasury, its NIM actually increased 2 basis points, helped by higher earnings on deposit and capital replicating portfolios, partly offset by lending competition and deposit impacts.

The broader NAB result was solid: revenue increased 2%, while cash earnings excluding the large notable item increased 2% compared with the first-half quarterly average.

But the comparison with CBA shows why NIM deserves particular attention. CBA is not merely generating more profit because it is larger. **It is earning materially more net interest income for each dollar of interest-earning assets.** That is a fundamental advantage in banking profitability.

| CBA FY26 vs NAB 3Q26                                                                                                                                                                                                                                                     |               |                     |                            |
| ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------- | ------------------- | -------------------------- |
| Indicator                                                                                                                                                                                                                                                                | CBA FY26      | NAB 3Q26            | Comparison                 |
| Reporting period                                                                                                                                                                                                                                                         | Full year     | June quarter        | Not directly like-for-like |
| Cash earnings / NPAT                                                                                                                                                                                                                                                     | $10.982bn +7% | $1.83bn +4% y/y     | CBA avg. quarter ≈ $2.75bn |
| Statutory profit                                                                                                                                                                                                                                                         | $10.866bn +7% | $1.81bn +9% y/y     | Both growing               |
| Pre-provision / underlying profit                                                                                                                                                                                                                                        | $16.469bn +6% | $2.9bn +6% y/y      | Similar core growth        |
| NIM                                                                                                                                                                                                                                                                      | 2.05% \-3bp   | 1.79% \-2bp\*       | CBA 26bp higher            |
| ROE                                                                                                                                                                                                                                                                      | 14.0% +50bp   | Not disclosed       | No direct comparison       |
| Operating expenses                                                                                                                                                                                                                                                       | $13.755bn +6% | $2.6bn +5% y/y      | Similar cost pressure      |
| Credit impairment                                                                                                                                                                                                                                                        | $788m +9%     | $299m +18% y/y      | Higher y/y for both        |
| CET1                                                                                                                                                                                                                                                                     | 12.0% \-30bp  | 11.93% +28bp vs Mar | Virtually identical        |
| Note: CBA figures are for the full year to June 2026\. NAB figures are for the June 2026 quarter. NAB year-on-year changes compare 3Q26 with 3Q25\. \*NAB headline NIM change is versus the 1H26 quarterly average; excluding Markets & Treasury, NAB NIM increased 2bp. |               |                     |                            |