This explains the mechanism — what an overdraft is and how the facility works. It is not advice about whether to use one, and it does not recommend any bank or product. Overdraft rules differ substantially between countries; the UK and US differ so much that the same word describes two different charging structures, and both are covered below.
What it actually is
An overdraft is permission to let the balance of a current account go below zero, up to some point, in exchange for interest or fees.
That is the whole thing. There is no separate account. The money is not transferred anywhere. Nothing is "drawn down". You use an overdraft by spending money you do not have in an account you already use for everything else, and the account simply reports a negative number.
This is why it does not feel like borrowing. Every other kind of credit announces itself — a card arrives, a loan pays into your account, a statement lands. An overdraft announces itself as a minus sign on a balance you were already looking at.
Why it isn't a loan
A loan and an overdraft are both credit, but almost every structural feature differs.
- A loan has a term. Three years, five years, whatever was agreed. An overdraft has none.
- A loan has a repayment schedule. A fixed amount leaves your account on a fixed day. An overdraft has no scheduled payment at all — it shrinks whenever money arrives and grows whenever money leaves.
- A loan is drawn down once. The money lands, and that is the debt. An overdraft is drawn and repaid continuously, often several times a day, without you noticing either event.
- A loan's balance only falls. An overdraft balance moves in both directions for as long as the account is open.
- A loan ends. An overdraft can sit on an account for decades.
That last point is the one that matters financially. A loan is designed to be extinguished. An overdraft is designed to be available, and something designed to be available tends to be used.
Why it isn't a credit card either
Credit cards are the closer comparison, and people often assume the two behave alike. Three differences change the arithmetic.
- No grace period, usually. A credit card cleared in full each month typically costs nothing in interest on purchases. An overdraft normally charges interest for every day you are below zero, including the first one. There is no equivalent of "pay it off before the statement and it's free" — although some accounts include a small interest-free buffer, which is a different thing.
- No statement of its own. A card sends you a monthly document showing the balance, the interest and the minimum payment. An overdraft appears as a line among your ordinary transactions, which is much easier to stop seeing.
- No minimum payment. That sounds like an advantage and often is not. A minimum payment is a mechanism that drags a balance down over time, however slowly. An overdraft has no such mechanism, so a balance can sit at the same level indefinitely while interest is charged on it every single day.
The absence of a repayment mechanism is the defining risk of the product. Nothing in the design ever pushes the balance back to zero.
Two ways to be overdrawn
The single word "overdraft" covers two quite different situations, and banks use at least three pairs of names for them.
- Arranged — also called planned, or authorised. You and the bank agreed a limit in advance. Within that limit, payments go through and you are charged the agreed rate.
- Unarranged — also called unplanned, or unauthorised. There is no agreement, or you have gone past the agreed limit. Each payment is now a decision the bank makes one at a time: pay it and let you go further overdrawn, or refuse it.
Which one you are in changes the cost, the reliability of your payments and, indirectly, what a lender sees later. It is a big enough distinction that it has its own guide.
Repayable on demand
This is the term people are most surprised by, and it is usually written into the agreement in plain sight.
An overdraft is normally repayable on demand. The bank can require the whole balance back, and it does not need the borrower to have done anything wrong. There is no fixed end date because there does not need to be one — the facility exists until the bank decides otherwise.
In practice banks rarely exercise this without warning, and in many countries rules and codes of practice require notice and fair treatment before an overdraft is reduced or withdrawn. But the underlying structure is not a fixed-term borrowing, and treating it like one is a mistake. What that means in practice is worth understanding before you rely on the facility.
The UK and the US work differently
The word is the same and the products are not. If you read advice written for the wrong country, the numbers will not make sense.
In the UK, an overdraft is priced as interest — a single annual rate applied to the amount you are overdrawn, for the days you are overdrawn. Since rules introduced by the Financial Conduct Authority took effect in 2020, banks must charge a single interest rate rather than daily or monthly fixed fees, and may not charge more for unarranged borrowing than for arranged. Rates are quoted as an EAR.
In the US, the dominant structure is a flat fee per item that takes the account below zero, rather than interest on the balance. Separately, banks offer "overdraft protection" services that link a savings account or line of credit to cover shortfalls, usually for a smaller transfer fee. Federal rules require customers to opt in before a bank may charge overdraft fees on everyday debit card and ATM transactions.
So "how much does an overdraft cost" has two structurally different answers. In one country the answer scales with how much and how long; in the other it scales with how many transactions.
How you end up with one
Very few people apply for an overdraft in the way they apply for a loan. The common routes:
- It came with the account. Many current accounts are opened with a small facility already attached, or offer one after a few months of use.
- It was offered in the app. A prompt, two taps, and it is live.
- It was a student account feature that never went away, and quietly converted to a charging one after graduation.
- You never had one. You simply spent past zero, the bank paid the item anyway, and you were unarranged without ever agreeing to anything.
That last route is the one that catches people, because nothing was agreed and no decision was made. The facility was used before it existed.
What to check on your own account
- Do you have an arranged limit, and what is it? It is in the account details in your banking app, usually under the account name rather than in the transaction list.
- What is the rate? One number, quoted annually. If your bank charges fees rather than interest, find the fee per item and the daily cap.
- Is there an interest-free buffer, and how large? Some accounts do not charge on the first small amount.
- How many days a month are you below zero? Not whether you go overdrawn — how long you stay. That is what the cost is calculated on.
- Is the balance returning to positive at any point in the month? If it never does, the overdraft has become a permanent debt with no repayment mechanism, and that is worth noticing early.
An overdraft is not a product you take out — it is permission for a current account you already have to hold a negative balance, and that is why it rarely feels like debt. It has no term, no repayment schedule, no statement of its own and no minimum payment, which means nothing in its design ever pushes the balance back to zero. It is normally repayable on demand, so the absence of a due date is not the same as having no deadline. And the word describes two different charging structures depending on where you are: interest on the balance in the UK, a flat fee per item in the US.
Sources
- Consumer Financial Protection Bureau (US) — What is an overdraft?
- Financial Conduct Authority (UK) — The UK financial services regulator