How Banks Work: APY, Fees and Deposit Insurance

Banking is the plumbing under every other financial decision, and almost nobody is taught how it works. That gap costs people real money — in fees they did not notice and interest they never earned.

What a bank does with your deposit

When you deposit money, the bank does not put it in a box with your name on it. It lends most of it out — mortgages, car loans, business loans — and keeps enough available to meet everyday withdrawals.

The bank's business is the gap between what it pays you and what it charges borrowers. That single sentence explains almost everything else: why deposit rates are lower than loan rates, why banks compete for deposits when lending is profitable, and why your balance is still yours even though it has been lent out.

It also explains why deposit insurance exists.

Deposit insurance

The FDIC insures deposits at insured banks. The standard coverage amount is $250,000 per depositor, per insured bank, for each account ownership category. Credit unions have comparable coverage through the NCUA.

Two details matter more than the headline number:

• Per bank, per category. A single person can be covered for more than $250,000 in total across different ownership categories, or by using separate insured institutions.
• Deposits only. Checking, savings, money market deposit accounts and CDs are covered. Stocks, bonds, mutual funds and crypto are not deposits and are not insured, even when bought through a bank.

The FDIC publishes a tool for checking whether a specific institution is insured and how coverage applies. It is worth five minutes if your balances are anywhere near the limit.

Interest rate vs APY

A savings account quotes two numbers that sound identical:

• Interest rate — the plain rate applied to the balance.
• APY (annual percentage yield) — the rate including the effect of compounding during the year.

Because interest is usually credited monthly and then earns interest itself, APY is slightly higher than the plain rate. APY is the number to compare, and it is the one that reflects what you actually receive.

Rates move with the wider interest rate environment, but the spread between banks is a business decision. Large branch networks are expensive; online-only banks frequently pay considerably more on the same kind of account.

Account types, briefly

• Checking — built for movement: debit card, bill payments, direct deposit. Usually pays little or no interest.
• Savings — built for storage. Pays interest, may limit certain transfers.
• Money market deposit account — a savings account with some checking features. Insured like a deposit; not to be confused with a money market fund, which is an investment and is not insured.
• CD (certificate of deposit) — a fixed rate for a fixed term, with a penalty for early withdrawal. Predictable, and not the place for money you might need suddenly.

The fees that quietly add up

Bank fees are disclosed but rarely read. The common ones:

• Monthly maintenance fees, often waivable with a direct deposit or minimum balance
• Overdraft and non-sufficient funds fees, charged when a payment exceeds the balance
• ATM fees, sometimes from both your bank and the machine's owner
• Wire transfer fees, on both sending and receiving
• Foreign transaction fees, typically a percentage of each purchase abroad

A $12 monthly fee is $144 a year — which, at a 4% APY, is what $3,600 of savings earns. Most of these are avoidable by choosing a different account, and the CFPB takes complaints when a bank gets one wrong.

Common mistakes

1. Leaving the emergency fund in checking, earning nothing and being spent by accident.
2. Comparing rate to APY instead of APY to APY.
3. Assuming everything at a bank is insured — investments bought through a bank are not.
4. Ignoring a monthly fee that a different account at the same bank would waive.
5. Keeping far above the insurance limit at a single institution without checking how the categories work.

A short checklist

• Confirm your bank is insured, and how your balances map to coverage categories.
• Compare your savings APY against a few online-only banks.
• Read the fee schedule once; it is usually two pages.
• Keep everyday spending money and savings in separate accounts.