What Does a Customs Broker Do? A Plain-Language Guide

Executive Summary 

What does a customs broker do? A good customs broker helps importers turn disorganized shipment details into accurate, compliant entries that can move through U.S. Customs with fewer delays. That means reviewing product data, classification, valuation, duties, documents, bonds, partner agency requirements, release status, and post-entry corrections. This plain-language guide explains where a broker fits, what your business still owns as importer of record, and how better brokerage support protects freight, cash flow, and compliance.

Intro 

Your customs broker files federal paperwork in your name, probably every week, and odds are you’ve never read a page of it. No judgment. Customs entries aren’t exactly page-turners.

In plain terms, a customs broker is licensed by U.S. Customs and Border Protection (CBP) to clear imports on your behalf, which is exactly as glamorous as it sounds.

The catch is that it’s all filed under your name, like a tax return: your accountant fills it out, you sign it, and the IRS writes to you.

Since June, CBP’s version also costs more. An executive order told CBP to stop knocking penalties down by more than half, ending the fine art of talking a fine into a rounding error.

So with that said, it’s worth knowing what goes out under your name. The job comes in five pieces, in the order your freight moves: building the entry, calculating the duty, handling the paperwork, dealing with holds, and protecting your record. 

None of it is complicated. But all of it can get expensive.

How Does a Customs Broker Build a Customs Entry?

A customs broker builds a customs entry by turning your shipping paperwork into a filing that tells CBP what you’re importing and what you owe. It takes four steps:

1. Collect the paperwork: Invoice, packing list, and bill of lading.
2. Classify each product: A clear description and a 10-digit tariff code.
3. Declare value and origin: What you paid and where it was made.
4. File with CBP: Up to five days before an ocean shipment arrives.

CBP reviews the filing, not the cargo, so your supplier’s invoice does the talking. "Parts" is a fine description for a bookkeeper in Ningbo. But to CBP it’s a question, and your container sits until someone answers it.

A good broker catches that and sends the invoice back before filing. It’s an awkward email, and a lot cheaper than the storage bill.

How Does a Customs Broker Calculate Import Duties?

A customs broker calculates import duties by finding each product’s duty rate through its tariff code and multiplying it by the declared value. A $100,000 shipment at 5% owes $5,000 plus any extra tariffs on that code, so both numbers have to be right.

The tariff code is a 10-digit number from the Harmonized Tariff Schedule, and CBP applies it with the literal-mindedness of a vending machine. When Section 338 tariffs on Canadian goods expanded in September, the bedside-lamp code landed on the list for cars, so those lamps pay the same extra 50% as a minivan out of Windsor.

Value is trickier, since CBP counts costs the invoice leaves out. Ship a $40,000 mold to your factory, and part of its cost belongs in the value of everything it makes. Customs calls that an "assist," and most importers first hear it from an auditor.

Good brokers ask about tooling before your first entry, and if yours never has, ask why.

What Documents Does a Customs Broker Need?

A customs broker needs two sets of documents: setup paperwork you sign once, and shipping paperwork for every load.

Before your first import:

• A power of attorney, letting the broker file in your name
• Your importer registration (Form 5106), so CBP knows who you are
• A customs bond, which guarantees CBP gets paid

With every shipment:

• The commercial invoice and packing list from your supplier
• The bill of lading or air waybill from your carrier
• An Importer Security Filing before ocean freight loads
• Agency paperwork for regulated goods, like FDA data

The setup documents are the ones importers sign and forget, and 2026 made forgetting expensive. Bonds usually run 10% of last year’s duties, so when tariffs tripled a duty bill, the bond fell short, and CBP set a deadline to fix it.

Since September 18, CBP can also cancel importer numbers whose registrations list the broker’s contact details, which is how plenty of brokers filled them out.

What Happens When Customs Holds Your Shipment?

Customs blocks delivery until CBP reviews your paperwork or inspects the cargo and authorizes release. Your broker should explain what’s needed and handle the response.

“CBP needs a spec sheet” is a different phone call from “they need to unload your container for an intensive exam.” The latter can mean trucking and handling costs on your bill, plus storage charges while you wait. Release times depend on the hold.

Your broker should also check when free time expires and coordinate pickup changes with the trucker and warehouse. If the same company handles customs and freight, you shouldn’t become the unpaid messenger between its departments.

So before hiring a broker, ask: if CBP holds my container at four on a Friday, when do I find out? Any answer with Monday in it is your answer.

What Does a Customs Broker Do After Freight Clears?

More than you’d think. 

Once the container’s gone, the broker files the entry summary, pays the duty, and minds the entry until CBP finalizes it about ten months later. Before that, mistakes get fixed quietly. After that, you’ve got 180 days to protest, then it’s final, right or wrong.

Ask anyone who chased an IEEPA refund this year. When the Supreme Court threw out those tariffs in February, roughly $166 billion in duties came up for refund, and the government started paying it back, receipts first.

Importers with clean entries uploaded a spreadsheet and had money within 90 days. The ones with disorganized entries spent the summer reconstructing 2025, some with a broker they’d already fired.

Keep those entries, too: they’re your audit file for five years, and CBP is auditing more. Clean records from 2024 are why a 2027 audit takes a week instead of a quarter.

Where Mallory Alexander Fits In

So, what does a customs broker do? On a good shipment, nothing visible. The entry beat the ship, the duty was right, the box left on day two, and everything stayed quiet. In this business, boring is the goal.

The shipments you remember are the loud ones, with the same cast: broker, forwarder, trucker, and warehouse at four companies, plus a Friday hold that becomes a reply-all about whose problem it is. The container waits for the thread to end.

Mallory Alexander International Logistics has cleared freight for 100 years and keeps those four jobs inside one company. Our licensed, CTPAT-validated brokers sit with the people who book the ocean, run the trucks, and manage the warehouses across 31 locations, so whoever reads the hold can fix the delivery. myMALLORY then shows it on one screen.

If it’s been a while since anyone looked at your tariff codes, bond, or importer record, get in touch. CBP is asking, and it’s cheaper to answer your broker than an auditor.