How does the repo rate imply a financing cost for bond positions, and when does an arbitrage opportunity exist?

Repo (repurchase agreement) financing is the backbone of the fixed income market, and understanding the implied financing rate is essential for Level II.

Repo Basics:

A repo is economically a collateralized loan:

1. Bond dealer sells a bond to a counterparty (lender) for cash
2. Dealer agrees to repurchase the same bond at a slightly higher price
3. The price difference is the repo interest (the cost of borrowing)

Repo Rate = [(Repurchase Price - Sale Price) / Sale Price] x (360/days)

The Implied Financing Rate:

When a trader buys a bond using repo financing, the cost of carry is:

Carry = Bond Yield - Repo Rate

If carry is positive (bond yield > repo rate), the leveraged position generates income. If negative, the position costs money to maintain.

Worked Example:

Quantum Fixed Income buys $100M face of the 10-year Treasury yielding 4.20%. They finance it in the overnight repo market at 4.05%.

• Daily carry = (4.20% - 4.05%) x $100M / 360 = $41.67 per day
• Monthly carry ≈ $1,250
• Annual carry = 15 bps on $100M = $150,000

But the trader also has duration risk. If the 10-year yield rises 20 bps, the price loss on $100M with duration ~8 is:

Loss = $100M x 8 x 0.0020 = $1.6M

The positive carry is dwarfed by potential rate risk.

Special Repo Rates and Arbitrage:

Some bonds trade 'special' in the repo market — meaning their repo rate is significantly below the general collateral (GC) rate. This happens when:

• The bond is in high demand for short-selling
• The bond is needed for settlement (fails would be costly)
• The bond is the 'cheapest-to-deliver' in a futures contract

Arbitrage from Specials:

This is the 'repo special spread' arbitrage. The trader earns 250 bps risk-free by lending the scarce bond and borrowing at a subsidized rate.

Implied Financing Rate for Futures:

The futures-implied repo rate is the financing cost implied by the relationship between the bond's cash price and the futures price:

Implied Repo = [(Futures Price x Conversion Factor + Accrued Interest at Delivery) / (Cash Price + Accrued Interest Now) - 1] x (360/days)

If the implied repo rate > actual repo rate: Buy the bond, sell the futures (cash-and-carry arbitrage)

If the implied repo rate < actual repo rate: Sell the bond, buy the futures (reverse cash-and-carry)

Exam Tip: Know how to calculate carry (yield minus repo), understand why some bonds trade special, and be able to identify cash-and-carry arbitrage from comparing implied and actual repo rates.

Master fixed income financing in our CFA Level II course.