Hypothetical worked example and primary educational references; not observed market data.
A fixed fee and a percentage yield scale differently
Interest based on a percentage grows with the balance, while a fixed account fee stays the same currency amount until its conditions change. US account-disclosure rules identify fees and relevant conditions, making them important inputs to a comparison. This scaling difference means the same account can have a much heavier proportional cost for a small balance than for a large one. A quoted yield alone does not capture that effect. Begin with the actual fee schedule and the balance path the saver expects. A fee that appears modest as a standalone currency amount may materially offset interest on a small emergency fund, while the identical charge represents a smaller fraction of a larger balance.
Supporting references: 1. CFPB: Regulation DD account disclosures
Convert the charge to a clearly defined ratio
Multiply the monthly charge by twelve to obtain an annual currency total, then divide by the chosen balance and express the result as a percentage. The example uses an invented USD 4 monthly charge and opening balances of 1200 and USD 8,000. Both rows therefore contain the same fee amount, but the proportional burdens differ. The denominator is explicitly the opening balance. If the balance changes, that simple ratio does not describe every period's experienced cost. It is a comparison measure, not an official annual yield. Naming the denominator matters because dividing by closing balance or average balance would produce another valid ratio with a different interpretation.
Hypothetical worked example
The same annual charge on different savings balances
Model setup
Read these assumptions before comparing the scenarios.
- All monetary amounts in this example are hypothetical U.S. dollars (USD), not current prices, quoted account terms or observed market data. Percentages, counts, time periods and index levels retain their stated units.
- A hypothetical monthly maintenance fee is USD 4.
- Opening balances are 1200 and USD 8,000.
- Balances are held constant for the fee-ratio illustration; no waiver or other charge.
Calculated result (percent of opening balance per year)
- Fee burden on USD 1,2004.00
- Fee burden on USD 8,0000.60
Shared zero-based scale; negative values extend to the left.
- Lowest displayed value
- 0.60
- Highest displayed value
- 4.00
Hypothetical cases from the table below, in the stated units. Not market observations, a forecast or a recommended choice. Read the scenario assumptions before comparing.
| Hypothetical scenario | Calculated result (percent of opening balance per year) |
|---|---|
| Fee burden on USD 1,200 | 4.00 |
| Fee burden on USD 8,000 | 0.60 |
Calculation details
- Fee burden on USD 1,200
- 4.00 percent of opening balance per year
(((4 * 12) / 1200) * 100) - Fee burden on USD 8,000
- 0.60 percent of opening balance per year
(((4 * 12) / 8000) * 100)
Net interest depends on the fee dates
For a rough one-year comparison, hypothetical gross interest minus the annual fee total can indicate whether earnings cover the charge. An exact model must also account for when fees leave the interest-bearing balance. A fee deducted early removes money that would otherwise have earned later interest. Subtracting all fees only at year-end overlooks that exposure effect. With monthly charges and growth, update the balance sequentially each month. The table avoids that complexity by reporting only the annual fee-to-opening-balance ratio. Its limited purpose is to expose the scaling mechanism, not calculate a complete net account return. This boundary keeps the simplicity useful without presenting the ratio as a precise reconstruction of a statement.
A waiver can change the comparison discontinuously
Some hypothetical account arrangements waive a charge when a balance or activity condition is met. Then the cost does not decline smoothly with balance; it may drop abruptly when the condition applies. The relevant measurement may be a daily minimum, a period average, or another contractual test. An opening balance above a threshold does not prove the charge will be waived if later withdrawals change the qualifying measure. Compare the expected balance path against the actual rule. Do not move money solely to meet an imagined threshold or assume a waiver is universal. The exercise's charge has no waiver, so its two rows isolate a fixed-cost ratio rather than describe the conditions of an existing product.
APY and spendable outcome need separate attention
CFPB's APY appendix provides an annualized interest framework. A saver comparing spendable outcomes should also track charges as distinct cash flows instead of assuming the headline percentage incorporates every cost. Use matching horizons and balances, and identify any fees that depend on expected transactions. The example offers no current account recommendation and makes no assertion that a particular institution charges USD 4. It teaches why fixed fees disproportionately affect smaller balances and why transparent units improve a comparison. A practical worksheet can show gross interest, fee total, timing effects, and net change separately. That presentation allows a reader to understand the tradeoff without allowing a single advertised yield or an unlabeled fee percentage to stand in for the complete result.
Supporting references: 2. CFPB: Regulation DD, Appendix A
Test another situationTest a fee on the cash actually left earning
A separate hypothetical case. Its inputs differ from the main worked example above.
Test a fee on the cash actually left earning
Suppose hypothetical USD 1,000 earns 1% per model month for two months, and an invented USD 10 charge is deducted after each month's interest credit. The first month ends back at USD 1,000, and so does the second. Without charges the balance would become USD 1,020.10. Fees remove USD 20 directly, while the total terminal gap is USD 20.10 because the first charge also loses a later earning opportunity. The high periodic rate is deliberately illustrative. The trade-off is a service carrying fixed charges against retained earnings; subtracting both charges only at the final date would miss their effect on the second month's base.
A fee ratio needs an exposure boundary
CFPB account disclosures identify fees and balance conditions. For comparing smaller and larger balances, state whether the denominator is opening principal, average balance, or the money actually available in each period. A fee-to-opening-balance ratio communicates burden but is not the same as a net compound yield. In a sequential model, place each charge after or before interest according to the stipulated terms and verify that a waiver has actually been earned. If the charge is paid from another account, include it in household costs even though it leaves the deposit's interest base untouched. Its location changes the interest effect, not whether it exists.
Supporting references: 1. CFPB: Regulation DD account disclosures
Check this case’s calculations
- Two-month fee path
- 1,000.00 USD
((((1000 * 1.01) - 10) * 1.01) - 10) - No-fee endpoint
- 1,020.10 USD
(1000 * (1.01 ^ 2)) - Direct charges
- 20.00 USD
(10 * 2) - Total fee-path difference
- 20.10 USD
((1000 * (1.01 ^ 2)) - 1000)
Limits of this additional case
- The monthly interest and deduction order are invented; actual charges and waiver conditions may follow different rules.
Limits of this analysis
- Actual fee waivers may depend on transactions or balance methods.
- Deducted fees can change later interest-bearing balances.
- This ratio is not a legally disclosed APY or a full net-return calculation.
Sources and scope
- CFPB: Regulation DD account disclosures
Covered account disclosures address rates, balance methods, fees, and time-account conditions.
Scope: US Regulation DD; educational discussion does not establish individual legal rights.. Reference accessed 2026-10-06.
- CFPB: Regulation DD, Appendix A
APY annualizes interest relative to principal and term under specified assumptions.
Scope: US covered deposit disclosures; not a universal account formula.. Reference accessed 2026-10-06.
Illustrative calculations are not forecasts or personal recommendations. Editorial standards
