Treasury Bill discount rate vs true yield: why the numbers differ

Overview
A Treasury Bill can be described with a discount rate, a holding-period return and an annualised investment yield. These measures answer different questions. The discount rate starts from face value, while the investor usually cares about return on the cash actually deployed. If a platform copies a stop rate and labels it simply as “yield”, it can overstate or understate what a customer should expect. SmartMoney separates the labels because financial decisions should not depend on a percentage whose denominator is unclear.

How it works in practice
The cleanest way to reason about a bill is to start with cash flows. Write down what leaves your account on settlement day and what is expected to come back at maturity. The difference is your nominal naira gain before charges. The holding-period return is that gain divided by cash invested. Annualising then introduces a time convention; that is useful for comparison, but it does not create extra cash. Market data services may publish yield measures that use standard money-market or bond-equivalent conventions, so the formula must be named whenever possible.

A practical process
1. Record face value, settlement price and days to maturity.
2. Compute the naira discount as face value minus purchase price.
3. Compute holding-period return using purchase price as the investment base.
4. If annualising, state the day-count convention and never mix it with a primary auction stop-rate label.
5. When comparing with a money-market fund or fixed deposit, compare cash timing, fees and liquidity as well as the annualised percentage.

Worked example
Illustrative example: if you invest ₦5,000,000 and the maturity proceeds are ₦5,700,000 after 364 days, the naira gain is ₦700,000 and the simple holding-period return is 14%. If someone instead quotes a rate calculated from face value or uses a different annualisation convention, the displayed percentage can differ even though the underlying cash flows are unchanged. Always reconcile the percentage back to naira.

Risks and limitations
- Rate-label confusion can cause a false comparison between instruments.
- Annualising a short holding period can make a modest naira gain look dramatic even though you cannot necessarily reinvest at the same rate.
- Fees or early-sale pricing can reduce the realised return.
- Screenshots without dates can mix different auctions or market sessions.

Verification checklist
Before acting, verify the exact product or security, the legal issuer or manager, the current date, the pricing or return methodology, the payment route, fees and liquidity terms. SmartMoney examples are educational and use simplified assumptions unless a dated source is explicitly named. Never transfer money because a screenshot, forwarded PDF or social-media message looks official. Navigate independently to the regulator, issuer, bank, broker, fund manager or merchant and reconcile the details.

Decision framework before comparing alternatives
A useful comparison keeps the time horizon and cash-flow basis consistent. Put every alternative on the same target date, write down the actual amount that leaves your account, estimate only cash flows that the product documents support, and list fees separately. If one option matures early, any assumed reinvestment rate is a scenario rather than a promise. If one option can fluctuate in market value, include a downside exit case. If liquidity differs, record the realistic number of business days required to get spendable cash. This framework prevents a higher-looking percentage from winning simply because it was calculated on a different denominator, tenor or reporting period.

Who should pause and verify further
Pause when the legal issuer or product is unclear, the payment destination differs from the verified institution, the return source cannot be explained, documents are undated, withdrawal terms are vague, or a seller creates urgency that prevents independent checks. Also pause when the investment would consume money needed for a known near-term obligation. A legitimate product can still be inappropriate for a particular cash-flow need, and a genuine institution can still be impersonated by a fraudulent channel. Verification is therefore both a product check and a transaction-channel check.

Records worth keeping
Save the current offer document, factsheet or source page; record the source date; retain the exact quote, fee schedule, payment evidence, transaction advice or contract note, ownership/custody record and expected maturity or redemption date. For market instruments, save the executed price rather than only the pre-trade quote. For funds, keep subscription and redemption confirmations. Good records make it possible to compare expected and realised returns, spot missing payments and resolve disputes without relying on memory. Store sensitive KYC and account material securely rather than forwarding it casually through messaging apps.

Frequently asked questions
Q: Which number should I care about most?
A: Start with cash invested, cash expected back and the exact dates. Percentages are most useful after those cash flows are clear.

Q: Is “true yield” an official universal term?
A: No. Different institutions may use different yield conventions; the formula or methodology should be identified.

Q: Can SmartMoney calculate my final bank proceeds?
A: It can illustrate calculations, but your institution must confirm actual price, charges, tax treatment and settlement.

Q: Why does a secondary-market yield differ from an auction rate?
A: Because the security can trade at a new price after issue and may have fewer days remaining to maturity.

Primary sources to verify
- Central Bank of Nigeria — Government Securities: https://www.cbn.gov.ng/rates/GovtSecurities.html
- FMDQ Group: https://fmdqgroup.com/

What changed?
This article was expanded for SmartMoney’s pre-index editorial review so it contains a complete decision framework, worked example, risk section, verification steps and primary-source links. Market-sensitive figures are deliberately not frozen into this guide; live or dated rates belong in SmartMoney’s source-labelled market cards. If an official rule, offer term or market structure changes, the article should be reviewed and the change recorded rather than silently rewritten.

Bottom line
Use this guide to ask better questions, not to outsource the decision. The correct transaction is the one whose current terms you can verify and whose risk, liquidity and cash-flow pattern fit the job your money needs to do. For regulated financial products, confirm current details with the appropriate official source and authorised provider before committing funds.