You spend in real time. Your bank settles in batches. That gap is where posting order lives, and it explains most of the confusing overdraft fees people get hit with on days when the arithmetic seemed to work.
When you swipe a debit card, the merchant sends an authorization request and your bank puts a hold on the money, but nothing has actually moved. The transaction sits pending. Later that night, after the bank’s cutoff time, everything that came in that day gets sorted and applied to your balance in one batch. The sorting rule is the posting order, and your bank chose it.
The order is written down, and it is not chronological by default
Every deposit account agreement contains a section on this, usually titled something like “order of payment” or “posting order.” It is one of the least read paragraphs in American consumer finance.
Most banks sort by transaction type first. Wire transfers and ATM withdrawals tend to clear before checks and ACH debits, which tend to clear before ordinary debit card purchases. Within each category, the bank picks a secondary rule: time received, dollar amount, or check number. Some categories post in the order the bank got them. Others post largest to smallest.
That last one has a history.
What high-to-low posting actually did
In 2007, a group of California customers sued Wells Fargo over the way it sequenced debit card transactions. Instead of posting them in the order they happened, the bank deducted the largest charge first, which drained the available balance faster and turned one overdraft into four or five.
The trial court was not subtle about what it found. The judge wrote that the bank’s dominant, and in fact sole, motive for choosing high-to-low posting was to maximize the number of overdrafts. Wells Fargo was ordered to pay $203 million in restitution, and the Ninth Circuit affirmed that judgment in 2014 while narrowing the injunction to debit card transactions.
A wave of similar suits followed against most of the large national banks. The practical result is that many big institutions moved to chronological or low-to-high sequencing for debit card purchases specifically. That is not a law, though. It came from litigation and settlements, and it does not necessarily cover checks, ACH payments, or the smaller banks and credit unions that were never sued. If you want to know what your bank does, the agreement is the only reliable source.
Why the sequence still costs money
The fee per incident has come down. Bankrate’s 2026 checking account survey puts the average overdraft fee at $26.77, a one percent dip from $27.08 the year before, with 94 percent of the accounts studied still charging something when the balance goes negative.
The aggregate is still large. Consumers paid roughly $12.1 billion in overdraft and non-sufficient funds fees in 2024, split between about $6.7 billion at banks and $5.4 billion at credit unions, based on Consumer Financial Protection Bureau data.
There was almost a federal ceiling on this. The CFPB finalized a rule in December 2024 that would have capped overdraft fees at $5 for institutions with more than $10 billion in assets, with an effective date of October 2025. Congress overturned it under the Congressional Review Act, and the President signed the repeal on May 9, 2025. No federal cap exists. What governs posting order today is the contract you agreed to when you opened the account, plus general state law on unfair and deceptive practices.
Credits, debits, and the cutoff time
Two more pieces of the sequence matter as much as the sort rule.
The first is whether credits post before debits on the same day. Most banks apply deposits first, which helps you. The catch is that “posted” and “available” are different states. Under Regulation CC, banks can hold portions of a deposit before releasing the funds, so a check you deposited Tuesday morning may be sitting in your account balance while being unavailable to cover Tuesday night’s batch.
The second is the cutoff. Every bank has a daily deadline, often somewhere between mid-afternoon and early evening, after which activity rolls to the next business day. Weekends and federal holidays are not business days. A Friday evening deposit and a Friday evening card swipe can both be labeled Monday, and they may not be labeled Monday in the order you expect.
This is also why your available balance and your current balance disagree. The current balance reflects what has settled. The available balance subtracts pending authorizations and unavailable deposits. Only one of those numbers is telling you what you can safely spend, and it is the smaller one.
Reading your own agreement
Pull up your bank’s deposit account agreement, which is almost always a PDF on the website, and search it for “posting” or “order of payment.” Three things are worth finding.
The sort rule tells you whether debit card purchases post chronologically or by amount. The daily fee cap tells you the maximum number of overdraft charges the bank will apply in one day, commonly three or four at large institutions, though some have dropped lower. The de minimis threshold tells you how far negative you can go before a fee triggers at all, and several major banks now skip the charge entirely if the account ends the day overdrawn by less than a set amount, often $50.
Those three numbers, together, determine whether a mistimed rent payment costs you nothing or costs you $80.
What to do with this
Posting order only matters when your balance is thin. When there is a cushion, the sequence is invisible, which is the strongest practical argument for keeping a buffer in checking rather than sweeping every spare dollar into savings the day it lands. A few hundred dollars parked in the account does no worse than earn a low rate, and it makes the entire question moot.
If you would rather keep that money working, the alternative is to link a savings account or an overdraft line of credit for automatic transfers, which usually costs far less per incident than a standard overdraft fee, and in some cases nothing.
The other habit worth building is watching the available balance instead of the current balance, and treating any pending transaction as already spent. Your bank does.
Posting order is not a scam so much as a rule you never negotiated. It is disclosed, it is legal, and it is written in your favor only by accident. Knowing which version your bank uses takes about five minutes and turns a category of surprise fees into a predictable one.