AU Small Finance Bank vs IDFC First Bank (2026): NIM, ROA, Growth & Which Is Better?

AU Bank vs IDFC First: Q1 FY2027 scoreboard

AU is still a high-spread secured-lending franchise

Its roots are in vehicle and small-business finance rather than low-yield corporate banking.

The current portfolio remains heavily oriented toward granular retail and commercial borrowers.

Q1 secured business grew approximately 25% year on year.

Unsecured business grew only 11%.

This distinction matters.

AU is not generating 23% total loan growth by aggressively expanding only unsecured personal credit.

Secured growth can support both yield and recoverability

Important AU lending categories include:

• Vehicle finance.
• Mortgages.
• Commercial banking.
• Small-business lending.
• Gold loans.
• Secured rural lending.

Collateral does not eliminate credit risk.

It can reduce loss severity when underwriting goes wrong.

That is particularly valuable in borrower segments where formal income documentation may be weaker than in salaried prime banking.

AU's loan growth is faster than IDFC First's despite being smaller

Gross loan portfolio increased 23% to ₹1.44 lakh crore.

IDFC First grew approximately 20.6% to ₹3.05 lakh crore.

AU is therefore expanding faster in percentage terms from roughly half the asset base.

This allows the bank to compound more quickly if its return ratios remain intact.

The disbursement engine is moving even faster

AU reported approximately 42% year-on-year growth in disbursements.

Management attributed part of the increase to growing contribution from newer geographies.

That means AU is not simply deepening Rajasthan and its older strongholds.

It is trying to build a broader national origination engine.

New geography is both AU's opportunity and its hidden underwriting test

Credit models often look strongest in markets where a lender has decades of local data and collections experience.

Moving into newer states can change:

• Borrower behaviour.
• Dealer relationships.
• Collateral resale values.
• Collection effectiveness.
• Competitive pricing.

The correct growth metric therefore is not only disbursement.

It is future slippage by vintage and geography.

So far, slippages are moving in the right direction

Q1 slippages declined approximately 22% year on year to ₹798 crore.

Credit cost including the CGFMU premium improved to about 0.8% from 1.4% a year earlier.

That is a large improvement.

It explains why AU's 5.9% NIM translates into much more profit than it did during the tougher microfinance cycle.

AU's asset quality is still weaker than IDFC First's

GNPA was 2.10% and NNPA 0.76%.

IDFC First reported 1.51% and 0.44%.

This prevents investors from treating AU's 1.7% ROA as a free lunch.

The bank earns more partly because its lending model produces a wider spread.

That wider spread exists partly because customer and product risk is not identical to a prime universal bank.

The bank is provisioned reasonably strongly against those risks

Provision coverage stood around 85% including technical write-offs.

Total capital adequacy was 18.9%.

Tier-1 was 17.1%.

AU therefore enters its next expansion phase with a large capital buffer.

Capital matters more because AU is still growing above 20%

A bank growing its risk-weighted assets rapidly consumes regulatory capital even when loans perform perfectly.

AU's 17.1% Tier-1 ratio gives it considerable capacity to continue growth before new equity becomes necessary.

IDFC First's current capital ratios are adequate but offer less headroom.

IDFC First's CASA balance is larger than AU's entire deposit base

IDFC First CASA deposits were approximately ₹1.58 lakh crore.

AU total deposits were approximately ₹1.58 lakh crore.

This is a useful illustration of the scale difference.

IDFC's low-cost funding pool alone is roughly as large as AU's complete deposit franchise.

Then why doesn't IDFC First dominate profitability?

Because liability quality is only one part of a bank's economics.

IDFC spends much more operating the franchise.

It also currently absorbs greater provision expense relative to loans.

Those two leakages consume much of the value created by its extraordinarily high CASA ratio.

70.7% cost-to-income is the number IDFC shareholders need to obsess over

The bank currently spends more than 70 paise to generate ₹1 of operating income before provisions and tax.

AU's approximate ratio is closer to the mid-50s.

This difference is enormous.

IDFC's cost base reflects years of investment in:

• Branches.
• Digital banking.
• Credit cards.
• Rural distribution.
• Wealth products.
• Payments.
• Customer acquisition.
• Corporate banking infrastructure.

IDFC's entire investment case can be reduced to operating leverage

If revenue grows 20% while costs grow materially slower, ROA can rise without any increase in NIM.

The bank already has the spread.

It already has the CASA franchise.

It already has scale approaching ₹3 lakh crore on both sides of the balance sheet.

Now those assets need to produce more profit.

The credit-cost burden is the second leakage

IDFC First provisions represented approximately 1.53% of average loans in Q1.

The recent microfinance downturn is a major contributor.

The bank has aggressively reduced its MFI exposure and substantially increased CGFMU protection.

If credit cost normalises, a large portion of current pre-provision economics can reach PAT instead.

This is why IDFC First's 132% profit growth should not be dismissed as a freak quarter

Some of the growth reflects recovery from a weak MFI-affected base.

But the operating franchise is also expanding:

• NII +21.1%.
• Loans +20.6%.
• Customer deposits +16.6%.
• CASA +24.6%.

The recovery therefore contains both base effect and genuine franchise growth.

AU currently monetises high NIM much better

AU earns 1.7% ROA from 5.9% NIM.

IDFC First earns 1.06% ROA from 5.96% NIM.

That is a 64-basis-point ROA difference from practically identical interest margins.

At banking scale, 64 basis points is enormous.

ROE makes the gap even clearer

AU: 15.6%.

IDFC First: 8.98%.

AU is already producing an ROE that many private banks would consider economically healthy.

IDFC First is still earning below the level normally needed to justify a large long-term premium to book value.

IDFC First can close the gap without becoming riskier

The cleanest route is lower expense and lower provisions—not higher NIM.

That is an attractive feature of the thesis.

The bank does not need to stretch for 7% NIM.

It needs to turn its current 6% margin into a more efficient bottom line.

Why would universal-bank status matter?

The strategic value is flexibility rather than an instant jump in earnings.

AU's roots in the small-finance-bank framework shaped its lending toward inclusion, granular borrowers and priority sectors.

A universal banking framework can over time allow the institution to compete more freely across:

• Larger corporates.
• Transaction banking.
• Trade finance.
• Affluent banking.
• International banking.
• Broader treasury relationships.

That could diversify the franchise.

It could also dilute the very high asset yields that currently support AU's 5.9% NIM.

Universal banking therefore creates a margin paradox

More diversification can make AU safer and larger while reducing NIM.

A corporate working-capital loan may carry a much lower spread than a small-ticket vehicle or business loan.

But the corporate relationship may also create:

• Current accounts.
• Trade fees.
• FX revenue.
• Cash-management fees.
• Employee banking.

AU's future should therefore be judged on ROA and ROE, not whether NIM stays permanently near 6%.

IDFC First already illustrates that wider product breadth does not guarantee high ROE

IDFC First today looks much more like a full-service universal banking franchise.

It has consumer banking, corporate banking, cards, rural lending, wealth, deposits and payments.

The challenge has been absorbing the cost of building all of those businesses simultaneously.

AU investors should therefore avoid assuming that broader universal-bank capabilities automatically improve profitability.

Which bank is growing deposits faster?

AU: 24%.

IDFC First: 16.6% customer deposits.

AU currently wins the percentage-growth comparison.

IDFC adds more deposits in absolute rupees because its base is much larger.

AU's cost of funds remains much higher

Approximately 6.48% versus IDFC First around 5.96%.

Yet AU still generates virtually the same NIM.

This again demonstrates the strength of AU's asset yield.

It also demonstrates the risk:

If competition pushes AU's loan yields lower faster than funding costs fall, margin can compress quickly.

IDFC's 50% CASA creates more protection against such repricing

A larger pool of low-cost liabilities gives management more pricing flexibility.

IDFC can theoretically compete more aggressively for high-quality borrowers while retaining a reasonable spread.

The question is whether it can do so while maintaining the existing 6% NIM.

AU's asset quality is improving at the right time

Slippages fell 22% and credit cost improved to 0.8%.

This matters because the market has already rerated the stock aggressively.

High valuation requires both growth and stability.

A return to elevated microfinance-like credit losses could quickly undermine the current premium.

IDFC First's asset-quality ratios look better today

GNPA 1.51% and NNPA 0.44% versus AU at 2.10% and 0.76%.

The comparison is not perfect because product mixes differ.

It still gives IDFC a meaningful current advantage.

Capital flips the comparison back toward AU

AU total capital is 18.9% and Tier-1 17.1%.

IDFC First total capital is about 15.05% and CET1 13.33%.

AU therefore has more capital headroom to absorb rapid growth or unexpected credit stress.

The valuation comparison is the opposite of the profitability comparison

AU currently earns much higher ROE but also trades at much higher P/B.

Fresh August 28 market data:

• AU P/E: ~28.3x.
• AU P/B: ~3.94x.
• IDFC First P/E: ~31.1x.
• IDFC First P/B: ~1.48x.

The earnings multiples are relatively close.

The book multiples are not.

Why does AU deserve almost 4x book?

Because current ROE is already 15.6% and growth exceeds 20%.

A bank compounding book value quickly at mid-teens ROE can deserve a premium if that return is sustainable.

The problem is that 4x book leaves little tolerance for:

• Credit-cost spikes.
• Margin compression.
• Universal-bank execution mistakes.
• Growth slowing toward industry levels.

Why is IDFC First only around 1.5x book?

Because current ROE is still below 9%.

The market has heard the long-term operating-leverage story for several years.

It now requires measurable movement in:

• Cost-to-income.
• Credit cost.
• ROA.
• ROE.

IDFC's valuation becomes very different if ROE reaches 15%

A 1.5x book bank earning 15% ROE is economically very different from a 1.5x book bank earning 9%.

That is the optionality investors are paying for.

The risk is that operating leverage takes longer than expected.

AU's valuation requires the reverse assumption

Investors must believe current 15%-16% ROE is durable while book value compounds rapidly.

If ROE falls toward 12%, the justification for a roughly 4x book multiple becomes much weaker.

The Bull Run price snapshot shows how strongly AU has rerated

AU was already very close to its 52-week high in the Bull Run snapshot.

The market is not treating the bank as an undiscovered turnaround.

It is treating it as a proven growth franchise.

What would make AU continue compounding?

• Deposit growth remains above 20%.
• Secured growth stays stronger than unsecured growth.
• NIM remains above roughly 5.5% even as the bank diversifies.
• Credit cost remains below 1%.
• ROA remains around 1.7%-2%.
• ROE remains mid-teens or better.
• Universal-bank transition is completed without disrupting the franchise.

What would make IDFC First close the profitability gap?

• Cost-to-income moves toward the low-60s.
• MFI provision burden normalises.
• CASA remains near 50%.
• Loan growth stays high-teens.
• ROA moves above 1.3%.
• ROE rises into double digits and then toward the mid-teens.

AU Bank vs IDFC First Bank FAQs

Which is growing loans faster?

AU Small Finance Bank, at approximately 23% year on year versus IDFC First Bank at 20.6%.

Which is growing deposits faster?

AU at approximately 24% versus IDFC First customer-deposit growth of 16.6%.

Which has the better CASA ratio?

IDFC First Bank by a wide margin, at 50.8% versus AU at 29%.

Which has the higher NIM?

IDFC First reported 5.96% versus AU at 5.9%, effectively a tie.

Which has the higher ROA?

AU at 1.7% versus IDFC First at 1.06%.

Which has the higher ROE?

AU at 15.6% versus IDFC First at 8.98%.

Which has better asset quality?

IDFC First currently has lower GNPA and NNPA ratios.

Which is better capitalised?

AU on current regulatory capital ratios.

Has AU become a universal bank already?

No. It received in-principle RBI approval and submitted its final application, but final approval remains pending as of August 31, 2026.

Which stock is cheaper on price-to-book?

IDFC First by a very large margin, around 1.5x book versus AU near 4x.

Where can investors check Bull Run data?

Use the AU Small Finance Bank stock page and IDFC First Bank stock page.

Research sources

• Bull Run — AU Small Finance Bank
• Bull Run — IDFC First Bank
• AU Small Finance Bank official investor overview
• AU Small Finance Bank official quarterly reports
• AU Small Finance Bank official exchange disclosures
• IDFC First Bank official financial reports
• IDFC First Bank Q1 FY2027 investor presentation