APY can look like a small number tucked beside a savings account name. But it answers a useful question: how much does a deposit earn over a year when compounding is included? Knowing what the number captures, and what it leaves out, makes account disclosures easier to read.
What does APY measure?
APY stands for Annual Percentage Yield. Regulation DD, the federal Truth in Savings rule, uses it to express the rate of return on a deposit account. The rule is meant to help people compare deposit accounts using one consistent measure. A headline interest rate may not show the effect of compounding.
The official calculation is set out in Appendix A to Part 1030. In plain terms, APY represents what a deposit earns over a year under the rule's calculation. It is a yield. It is not simply the stated interest rate printed on an account page.
Why does that distinction matter? Interest is added to a balance, and then that added interest can earn interest too. That process is called compounding. APY accounts for compounding over a year, which is why it can differ from a simple annual rate. The actual growth in your account depends on the account's terms and the amount you deposit.
An illustrative example with made-up numbers
The sources linked here do not reproduce a worked example, so the figures below are hypothetical and for illustration only. Appendix A holds the official method, and the CFPB and FDIC consumer pages are good places to confirm how it applies to a real account.
Say an account pays a stated rate of 4.00% a year, with interest compounded daily. The common compound growth idea is that each day's interest is added to the balance, so the next day's interest is figured on a slightly larger amount. Over a full year, that pushes the effective yield a little above 4.00%. Under that simple math, the result lands near 4.08%. That 4.08% is the kind of figure APY is meant to express.
On a hypothetical $1,000 deposit with no withdrawals, that gap is roughly 80 cents over a year. Small, but it shows the mechanism. The more often interest compounds, the larger the gap between the stated rate and the APY, all else equal. The sources do not cover how compounding frequency changes results, so treat this as a rough sketch and not a promise.
What should the disclosure show?
Regulation DD requires financial institutions to disclose the APY and related account terms. The rule covers more than the opening paperwork. It also addresses periodic statements, payment of interest, advertising and overdraft disclosures. Those requirements are intended to make deposit account terms visible before and after an account is opened.
The rule appears in 12 CFR Part 1030. It was most recently amended on April 19, 2023, according to the CFPB's regulation text. The FDIC's Truth in Savings examination manual gives examiners guidance for reviewing whether institutions follow the rule. APY disclosure is part of a federal disclosure framework. It is not just a habit of account marketing.
How can you check an advertised APY?
Start by looking for the APY in the account disclosure, along with the terms that apply to it. Then compare that figure with the APY shown in any advertisement. Advertising that shows a rate without the required APY and related terms may not meet Regulation DD's advertising rules. A mismatch is worth raising with the institution.
Use the current disclosure. Do not rely on an old screenshot or a number you remember from an ad. Rates and advertised figures can change. The sources here do not explain how variable rates are handled over time, so the disclosure is the place to check what currently applies.
Questions worth asking:
- Does the disclosure state the APY and the terms attached to it?
- Does the advertised APY match the account documents?
- Do the two accounts you are comparing have comparable terms?
What can't APY tell you?
APY helps compare the yield on deposit accounts, but it does not answer every question about savings. The sources used here do not provide current national averages or typical APY levels. They also do not explain how interest is taxed, how APY relates to inflation, or how deposit insurance limits apply. Those are separate topics, and the APY figure alone cannot settle them.
A rate in an advertisement is not a promise that the same figure will apply indefinitely. Check the current account terms for the APY and conditions being presented. For broader questions about deposit accounts, the CFPB and FDIC offer consumer information. This article is educational, not personal financial, legal or tax advice.
So when a savings account puts a percentage in large type, look for the APY and its related terms. It works best as a common measuring stick for comparing accounts.
Please seek a professional. This article is general information, not financial, tax or insurance advice. Please seek a licensed financial, tax or insurance professional about your own situation.
