Cash Flow Matching

Cash-flow matching (also called dedicated portfolio strategy) aligns bond maturities and coupons with the exact timing and amount of known future obligations, eliminating reinvestment risk by letting bonds pay liabilities directly.

Key takeaways

• Buy bonds whose coupons and maturities precisely match your liability schedule: coupon due on payment date, principal due on final date.
• This is the simplest, most intuitive liability-matching strategy: no duration calculations, no rebalancing, no trading.
• Works best for multi-year, multi-payment liabilities (pension obligations, bond sinking funds, education funding).
• Eliminates reinvestment risk and interest-rate risk completely for the matched portion.
• More conservative than immunisation (requires less active management) but less flexible.

The principle: matching cashflows

A liability is a schedule of payments. A bond portfolio is a schedule of coupons and principal repayments. Cash-flow matching means the portfolio's schedule matches the liability schedule.

Example: College fund

Liability schedule:

• Year 8: 50,000 dollars (freshman year).
• Year 9: 50,000 dollars (sophomore year).
• Year 10: 60,000 dollars (junior and senior combined).
• Total: 160,000 dollars over 3 years.

Bond portfolio to match:

Bond	Maturity	Coupon	Semi-Annual Coupon	Principal	Total at Maturity
Bond A	Year 8	3.5%	1,750	50,000	51,750
Bond B	Year 9	3.7%	1,850	48,000	49,850
Bond C	Year 10	4.0%	2,000	60,000	62,000

The coupons of Bond A (1,750 × 2 = 3,500 total per year) plus principal (50,000) cover the year 8 expense exactly. Bond B covers year 9. Bond C covers year 10.

This is cash-flow matching: each bond "dedicates" its payoff to a specific liability.

Building a cashflow-matched portfolio

Step 1: List liabilities by date and amount.

Year	Payment
2028	30,000
2029	35,000
2030	40,000
2031	45,000

Step 2: Find bonds (or a blend) whose coupons + principal equal each payment.

This is an optimization problem. Ideally, a single bond matures on each payment date with a coupon schedule that fills in the gaps.

In practice, you may need a blend:

For the 2028 payment of 30,000:

• A bond maturing in 2028 with 20,000 principal + 10,000 in coupons collected through 2027.

For the 2029 payment of 35,000:

• A bond maturing in 2029 with 30,000 principal + 5,000 in coupons.

And so on.

Step 3: Verify the schedule.

Create a timeline showing:

• Each bond's coupon payments (semi-annual or annual).
• Each bond's maturity date and principal repayment.
• Sum each year's total inflows.
• Confirm they match liabilities.

Dedicated portfolio example: a pension fund

A pension fund must pay:

• 100,000 dollars/year for years 1–10 (fixed).
• 110,000 dollars/year for years 11–20 (slightly higher due to inflation assumption).

Total liability: (100,000 × 10) + (110,000 × 10) = 2,100,000 dollars.

The fund manager buys a mix of bonds maturing across 20 years such that:

• Year 1: Coupons and maturities total 100,000.
• Year 2: Coupons and maturities total 100,000.
• ...
• Year 10: Coupons and maturities total 100,000.
• Year 11: Coupons and maturities total 110,000.
• ...
• Year 20: Coupons and maturities total 110,000.

A simple approach: buy 20 bonds, each maturing in a single year (1-year, 2-year, ..., 20-year), with principal sized to cover most of the year's liability, and choose coupon rates such that the total inflow matches.

Or buy a ladder (multiple bonds per year) to smooth reinvestment and diversify credit risk.

Once the portfolio is built, the fund manager does no rebalancing (assuming bonds are held to maturity). Coupons and principal are collected on schedule and paid to pensioners.

Individual use: college funding

You have two children, each needing 100,000 dollars over four college years.

Child A:

• Age 17 (high school senior): enters college in 2027.
• Payments: 2027 (25,000), 2028 (25,000), 2029 (25,000), 2030 (25,000).

Child B:

• Age 15 (junior): enters college in 2029.
• Payments: 2029 (25,000), 2030 (25,000), 2031 (25,000), 2032 (25,000).

Combined liability schedule:

• 2027: 25,000.
• 2028: 25,000.
• 2029: 50,000 (both children).
• 2030: 50,000.
• 2031: 25,000.
• 2032: 25,000.
• Total: 200,000.

Build a portfolio:

• 4-year bond (matures 2027): principal 20,000, coupons 5,000 → covers 25,000 in 2027.
• 5-year bond (matures 2028): principal 20,000, coupons 5,000 → covers 25,000 in 2028.
• 6-year bond (matures 2029): principal 40,000, coupons 10,000 → covers 50,000 in 2029.
• 7-year bond (matures 2030): principal 40,000, coupons 10,000 → covers 50,000 in 2030.
• 8-year bond (matures 2031): principal 20,000, coupons 5,000 → covers 25,000 in 2031.
• 9-year bond (matures 2032): principal 20,000, coupons 5,000 → covers 25,000 in 2032.

To finance this portfolio, you need to invest approximately:

• Sum of all principals needed: 160,000.
• You will earn coupons: 40,000.
• But you need to invest upfront, so total upfront ≈ 160,000 to 180,000 (depending on coupon reinvestment and discounting).

Simplification: Assume a flat 3.5% yield curve. A bond with principal P, maturing in year T, purchased at par, costs P / (1.035)^T.

Total investment: 20k/1.035 + 20k/1.035^2 + ... + 20k/1.035^6 + 40k/1.035^6 + ... ≈ 150,000 to 160,000.

You invest roughly 150,000–160,000 dollars today; 10 years later, you have collected coupons and have all the principal to fund college.

Comparison: cashflow matching vs. laddering

Aspect	Cashflow Matching	Laddering
Liability specification	Known, exact schedule	General/ongoing income needs
Reinvestment risk	Zero (bonds held to maturity)	Managed (reinvestment at long end)
Rebalancing	None (passive)	Quarterly (maintain structure)
Flexibility	Low (locked into liability dates)	High (can adjust allocations)
Complexity	Medium (requires careful scheduling)	Medium (formulaic)
Suitability	Known, multi-year obligations	Income, growth, or undefined timeline

Cashflow matching is more appropriate when liabilities are known and fixed. Laddering is better for general income.

Advantages of cashflow matching

1. Certainty: You know exactly when cash is available. No surprise from market moves.
2. No reinvestment risk: You are not forced to reinvest coupons; they arrive on payment dates and are used immediately.
3. No rebalancing trades: Hold to maturity. Minimal fees and taxes.
4. Simplicity: Once built, the portfolio is passive. Just collect coupons and principal on schedule.
5. Immunisation: Because cashflows match exactly, you are completely immunised against interest-rate risk (for the matched portion).

Disadvantages of cashflow matching

1. Inflexibility: If liabilities change (your child decides not to attend college, or attends an extra year), you are locked into bonds that do not match.
2. Complexity of construction: Finding the exact bonds to match a complex liability schedule is time-consuming.
3. Suboptimal yield: You may sacrifice yield to achieve exact matching. A ladder might yield 4.6% average; cashflow matching might yield 4.3% (if you have to buy many short-term bonds to meet early payments).
4. Reinvestment of coupons: While principal is dedicated, coupons often arrive before they are needed. You must reinvest coupons at prevailing rates, reintroducing reinvestment risk.
5. Opportunity cost: If you overestimate liabilities, capital is locked in bonds earning 3–4% when stocks return 8–10% on average.

Hybrid approach: partialcashflow matching

To balance certainty with flexibility, some investors use partial matching:

• Core matched: Buy bonds to cover 70–80% of liabilities, with maturities matching each liability date.
• Flexible reserve: Keep 20–30% in a barbell or ladder for adjustments, growth, or contingencies.

Example: You need 200,000 dollars over 10 years (college and other expenses).

• Matched portion: 150,000 dollars in cashflow-matched bonds (75%).
• Flexible portion: 50,000 dollars in a 5-year ladder or barbell (25%).

If liabilities are lower than expected, the flexible portion grows. If higher, you tap the flexible portion.

Building a cashflow-matched portfolio in practice

Step 1: Define liabilities. Create a spreadsheet listing year, payment amount, and cumulative total.

Step 2: Source bonds. Use a bond broker or platform to search for bonds maturing in each year. Specify:

• Maturity date (must be in the liability year).
• Amount of principal needed.
• Minimum credit quality (A or better, unless you are comfortable with B-rated corporates).

Step 3: Calculate required coupon and principal. For each liability:

• Liability amount: L.
• Years until payment: T.
• Assume you will reinvest coupons at 3.5% (or your best estimate).
• Solve for required principal P and coupon C such that P × (1.035)^T + C × coupon factor = L.

This is an iterative calculation; most financial advisors use software.

Step 4: Verify schedule. Create a timeline:

• Semi-annual coupons for each bond.
• Maturity principal for each bond.
• Sum each year's total.
• Confirm it matches liabilities (within 1–2%).

Step 5: Purchase bonds. Buy the bonds, hold to maturity, and execute the schedule.

Real-world constraints

Bond selection: Finding bonds with exact maturity dates is often impossible. You may need to:

• Buy bonds maturing slightly before or after the liability date, and bridge with cash.
• Buy multiple bonds per liability year to aggregate to the exact amount.
• Accept some bonds maturing a year early (if you can hold them to the liability date without reinvestment risk).

Ladder blending: Many practitioners build a dedicated ladder—a ladder specifically designed for a liability stream. Each rung covers 1–2 years of liabilities, simplifying construction.

Tax considerations: In a taxable account, bonds bought at a discount and held to maturity are taxed on the accretion (the difference between purchase price and par), often as ordinary income. In a tax-deferred account (IRA, RRSP), this is not an issue.

When to use cashflow matching

Best for:

• Known, fixed, multi-year obligations (college, pensions, bond sinking funds).
• Investors who dislike active management.
• Investors in high tax brackets (holding to maturity is tax-efficient).
• Tax-deferred accounts (401k, RRSP, TFSA) where the tax benefits are clear.

Avoid when:

• Liabilities are uncertain or flexible.
• You need income flexibility (consider a ladder instead).
• Bonds are a small portion of a broader portfolio (construction complexity outweighs benefit).

Comparison to immunisation

Both cashflow matching and immunisation align assets to liabilities, but via different mechanisms:

Approach	Method	Rebalancing	Rate Risk	Complexity
Cashflow Matching	Exact maturity + coupon match	None	Zero	Medium
Immunisation	Duration match	Frequent	Near-zero (duration offset)	High

For individual investors with known obligations, cashflow matching is simpler and more intuitive. Immunisation is more flexible but requires ongoing monitoring.

Next

Cashflow matching uses maturity dates as the matching variable. Duration matching, the next article, uses duration—the weighted-average time to receive cashflows—as the primary control, allowing more flexibility in which bonds you choose while still matching liabilities precisely.

Related concepts

• Immunisation Strategy
• Duration Matching
• Laddering for Retirement Income