Your account number appears in the bottom left corner of the check, printed in magnetic ink
The account number on a check is located in the bottom left section, printed as a series of digits in magnetic ink (the same dark, slightly raised numbers used for the routing number). It sits between the routing number on the far left and the check number on the far right. On most checks, it is the longest string of numbers in that row.
When you deposit a check using your phone, the mobile deposit system reads these magnetic numbers automatically. You do not need to type them manually—the app captures them from the image you take. However, knowing where to find it helps you verify the deposit is being processed against the correct account if something goes wrong.
The account number identifies which specific account at your bank the check is drawn from. If you are depositing a check into your own account, this number tells your bank whose account to pull the funds from. If you are depositing a check written to you, your bank uses your own account number (stored in your profile, not on the check itself) to know where to deposit the money.
Key Takeaways
- The account number is the middle set of digits in the bottom left of the check, between the routing number and check number.
- Mobile deposit apps read the account number automatically from the check image, so you do not need to enter it by hand.
- The account number identifies which account at the bank the check is drawn from, not the account you are depositing into.
- If mobile deposit fails to read the numbers, you can manually enter the account number from the check to complete the deposit.
How the three numbers at the bottom work together
The bottom of every check contains three separate pieces of information printed in magnetic ink, read from left to right: the routing number, the account number, and the check number.
The routing number (usually nine digits) identifies which bank or credit union issued the check. The account number (typically 10 to 12 digits, but varies by bank) identifies the specific account within that bank. The check number (usually four digits) is a sequential identifier for that individual check. Together, these three numbers tell the banking system exactly where the money is coming from and which check it is.
When you photograph a check for mobile deposit, your bank's system reads all three numbers. The routing number tells it which bank to contact to pull the funds. The account number tells it which account at that bank to pull from. The check number helps track the transaction if there is a dispute later.
What happens if the account number is missing or unreadable
If the account number is smudged, faded, or partially obscured, mobile deposit may fail to read it. When this happens, the app usually displays an error message and asks you to re-photograph the check or enter the number manually.
If you cannot read the account number from the check image, you have two options: ask the person who wrote the check for the account number directly, or contact their bank with the routing number and check number to request the account information. Most banks will not provide this over the phone for security reasons, so the first option is usually faster.
In rare cases, a check may be printed without an account number—this sometimes happens with starter checks or checks printed by a third party. If this occurs, the check cannot be processed through mobile deposit and must be deposited in person at a branch or ATM.
Why banks print the account number in magnetic ink
The magnetic ink used for the routing number, account number, and check number is called MICR ink (Magnetic Ink Character Recognition). It allows high-speed machines to read the numbers automatically without human intervention, which is why checks can be processed so quickly even when thousands are deposited daily.
The same technology that reads checks at the bank also reads them when you use mobile deposit. Your phone camera captures an image of the check, and your bank's system uses optical and magnetic scanning to extract the three numbers from the bottom. This is why the image quality matters—if the photo is blurry or the lighting is poor, the system may struggle to read the account number.
The account number is also printed in regular ink elsewhere on the check (usually in the top right corner, next to the date), but this version is for human reference only. The magnetic version at the bottom is what the banking system actually uses.
Protecting your account number when depositing checks
Your account number is sensitive information, but it is already printed on every check you write. Anyone who receives a check from you can see your account number. This is a known risk of using checks, which is one reason many people prefer digital payment methods.
When you deposit a check using mobile deposit, your bank encrypts the image and the extracted numbers before transmitting them. The image itself is not stored permanently on your phone—it is deleted after the deposit is confirmed. Your bank's servers store the transaction record, but not the photograph.
If you are concerned about a check you have written being misused, contact your bank immediately. You can place a stop payment on that specific check, which prevents the funds from being withdrawn even if someone tries to deposit it. There is usually a small fee for this service (typically $25 to $35), but it provides protection if you believe the check was lost or stolen.
Reading the account number on different check styles
Most personal and business checks follow the same layout: routing number, account number, check number across the bottom in magnetic ink. However, some checks are printed differently depending on the bank or the type of account.
Cashier's checks and certified checks may have the account number in a different location or printed differently, since they are issued by the bank itself rather than printed by the account holder. Starter checks (temporary checks issued when you open an account) sometimes omit the account number entirely. Checks from credit unions follow the same standard as bank checks.
If you are unsure whether a check is legitimate or readable, photograph it anyway and attempt mobile deposit. If the system cannot read the numbers, it will tell you, and you can then contact the check writer or their bank for clarification.
Frequently Asked Questions
Can someone withdraw money from my account if they have my account number from a check?
Having only your account number is not enough to withdraw money. A person would also need your routing number (which is also on the check) and authorization from you. However, they could potentially write a fraudulent check or set up an unauthorized ACH transfer using both numbers. If you suspect fraud, contact your bank immediately to place a fraud alert on your account.
What if the mobile deposit app cannot read the account number?
Try retaking the photo with better lighting and a steadier hand, making sure the bottom of the check is in focus and fully visible. If the app still cannot read it, you can manually type the account number into the deposit form. The number is printed on the check in two places: in magnetic ink at the bottom and in regular ink elsewhere on the check.
Is the account number on a check the same as my online banking login?
No. Your account number is used for deposits and transfers, but it is not your login credential. Your online banking username and password are separate and should never be written on a check or shared with anyone.
Why does my check have two account numbers printed on it?
Most checks have the account number printed twice: once in magnetic ink at the bottom (for machine reading) and once in regular ink elsewhere on the check (for human reference). Both numbers are identical and refer to the same account.