The Treasury Book
The bond and investment portfolio beyond SLR — where rate moves become mark-to-market gains or losses.
Why you care
SLR forces a bank to hold G-secs; the treasury book is the bond portfolio it holds on top of that, to earn a return and manage liquidity. It's where the bank takes a view on rates — and where a rate move quietly becomes a profit or a loss before a single loan is touched.
Run the numbers
A bond portfolio with ~4-year duration loses roughly 4% of its value if yields rise 1% (illustrative). On a ₹10,000 cr book that's a ~₹400 cr mark-to-market hit — no default, just rates moving the wrong way.
Where this goes
When rates fall, the book throws off treasury gains that land in non-interest income and flatter a quarter. When rates rise, it bleeds MTM losses. It's the reason "other income" can swing so hard from one quarter to the next.
Why you care
The treasury book is a bank's portfolio of bonds and other investments. Part of it is the SLR G-secs the regulator forces it to hold; the rest is discretionary — bonds the bank buys to park surplus liquidity and earn a return. The treasury desk that runs it is where a bank stops being purely a lender and starts being a bond investor.
Here's why it matters on its own: this is where interest-rate risk lives. A loan book mostly cares about defaults; a bond book mostly cares about rate moves. Bonds are marked to market, so when yields rise, the price of the bonds the bank already holds falls, and the bank books a loss even though nothing defaulted. This is the "MTM pain on rising rates" that the SLR node hints at. It's a genuine source of quarterly volatility — a bad bond quarter can dent profit as surely as a bad loan quarter, just through a different door.
The book is split into buckets that decide how much of this volatility hits the P&L:
- HTM (Held to Maturity): bonds the bank intends to hold to the end. Not marked to market, so rate moves don't hit reported profit — most SLR G-secs sit here.
- AFS (Available for Sale): marked to market; gains and losses flow through, which is where rate-move volatility shows up.
- HFT (Held for Trading): actively traded for short-term gains.
Run the numbers
The key mechanic is duration — how sensitive a bond's price is to rate moves. A portfolio with a duration of ~4 loses about 4% of its value for every 1% rise in yields (illustrative).
Take a ₹10,000 cr AFS bond book:
- Yields rise 1% → price falls ~4% → ~₹400 cr mark-to-market loss, straight through the P&L.
- Yields fall 1% → ~₹400 cr gain, booked as treasury profit.
No borrower did anything. The entire swing came from the repo rate and the broader rate environment moving. This is why banks with big AFS books have a love-hate relationship with a rate-cut cycle. Falling rates hurt the lending margin through faster loan repricing, but hand the treasury desk a windfall of bond gains. The two partly offset — which is exactly the kind of thing that separates a reader who understands a results deck from one who panics at a single line.
Where this goes
The treasury book is the bridge between the rate environment and the bank's other income: its gains and losses are a core, and lumpy, part of that line. It grows out of the SLR G-secs the regulator forces and the bank's own view on where the repo rate is heading. When you see a bank's "other income" jump or crater in a quarter, the treasury book is usually the reason. That's also why analysts strip treasury out to judge the steadier fee engine underneath.