You packed the box carefully. You paid for shipping. You did everything right — or so you thought.

Then the tracking page stalls. "In Customs" sits there for three days, then five, then ten. Your recipient starts asking questions you can't answer, and somewhere in a bonded warehouse, your package is waiting on a piece of paperwork nobody told you about.

International shipping doesn't have to work this way. The vast majority of customs delays come down to a small, predictable set of mistakes — a wrong code here, a missing form there, a value that doesn't match the invoice. Once you know what customs officers are actually looking for, you can avoid nearly all of it.

This guide breaks down exactly why packages get stuck, what documents you actually need, who should pay the duties, and how to build a shipping process that clears customs the first time.

Why Packages Get Stuck in Customs (The Real Reasons)

Customs isn't trying to slow you down for sport. Every country's border agency — including U.S. Customs and Border Protection (CBP) — exists to verify that what's crossing the border is legal, safely declared, and correctly taxed. Delays happen when that verification can't happen smoothly. Here's what usually trips people up.

Missing or Incorrect HS (Harmonized System) Codes

Every product that crosses an international border needs an HS code — a standardized number from the Harmonized Tariff Schedule that tells customs exactly what's inside the box. Customs authorities use it to calculate duties and check for restrictions, so a missing or wrong HS code stops your shipment before it can even be assessed.

Common mistakes:

  • Using a vague, generic code instead of the specific one for your product
  • Guessing instead of looking it up
  • Reusing an old code for a product that's changed materials or use

A few minutes spent confirming the correct tariff classification can save days of delay.

Incomplete or Inconsistent Customs Forms

Customs officers cross-reference your paperwork. If your customs declaration form says one thing and your commercial invoice says another — different values, different item descriptions, different weights — that inconsistency is often enough to trigger a manual review.

The most common culprits are:

  • Vague descriptions like "gift" or "parts" instead of specific product names
  • Missing sender or recipient contact information
  • Quantities or values that don't match between documents

Under-Declared or Over-Declared Value

It's tempting to write a lower value on a customs form to reduce duties, but customs authorities are trained to spot mismatches between declared value and actual value — and the penalties for misdeclaration are far more expensive than the duty you were trying to avoid.

Over-declaring causes its own problems: it inflates your dutiable value, meaning you (or your recipient) pay more tax than necessary. Accuracy, not minimization, is the goal.

Prohibited or Restricted Items You Didn't Know About

Every destination country maintains its own prohibited items list and restricted items list, and they vary more than people expect. Items that ship freely domestically — certain foods, cosmetics, batteries, plant products, even some electronics — can be outright banned or require special permits elsewhere.

This is one of the most avoidable causes of delay, because the information is public. It just has to be checked before you ship, not after.

Random Inspections vs. Flagged Shipments — What's the Difference?

Not every hold means something is wrong. Customs agencies conduct routine random package inspection as a standard part of border security, regardless of what's in the box.

A flagged shipment is different — it's held because something in the paperwork, the declared value, or the product itself raised a question. Random inspections usually clear within a day or two. Flagged shipments can sit for much longer, because they require someone to review, and possibly contact you for clarification.

The Documents You Actually Need (And Where to Get Them Right)

Good paperwork is the single biggest lever you have over customs speed. Here's what actually matters.

Commercial Invoice vs. Customs Declaration (CN22/CN23) — What's the Difference for Everyday Shippers

These two documents get confused constantly, but they serve different purposes:

  • Customs declaration form (CN22/CN23): Used mainly for postal shipments (like USPS Priority Mail International). CN22 is for lower-value packages; CN23 is required for higher-value or larger shipments. It's a simplified summary of what's inside and its value.
  • Commercial invoice: Used for commercial shipments, especially through couriers like UPS, FedEx, or DHL. It's a more detailed record — itemized products, values, HS codes, and terms of sale — and it's what customs brokers and customs officials rely on to assess duties accurately.

If you're shipping a personal item through the postal service, you'll likely only need a CN22/CN23. If you're shipping for a business, expect to need a full commercial invoice, and often a packing list alongside it.

Certificates of Origin, When You Need One

A certificate of origin verifies which country your goods were manufactured in — not shipped from. This matters because many countries offer reduced or zero duties under trade agreements, but only if you can prove the rules of origin are met.

You'll typically need one when:

  • Shipping commercial goods to a country with a relevant trade agreement
  • The destination country's customs requires proof of manufacture for specific product categories
  • Your customs broker or freight forwarder flags it as required for your product and lane

If you're unsure whether your shipment needs one, it's worth checking before you ship rather than after your package is held.

How to Fill Out a Customs Form Correctly (Step-by-Step)

  1. Identify the correct HS code for each item using an official tariff classification lookup tool.
  2. Write specific, honest descriptions — "cotton t-shirt, men's" rather than "clothing" or "gift."
  3. Declare the actual value of the goods, matching your invoice or receipt.
  4. List quantity and weight accurately for each line item.
  5. Include complete sender and recipient details, including phone number and email where the form allows.
  6. Choose the correct shipment type (gift, sale of goods, sample, return, etc.) — this affects how customs treats the package.
  7. Double-check that every number matches across your invoice, packing list, and declaration form before you seal the box.

Who Pays the Duties and Taxes? DDP vs. DDU Explained Simply

This is one of the most misunderstood parts of international shipping — and one of the biggest sources of "surprise fee" complaints.

Delivered Duty Paid (DDP): Paying Upfront to Avoid Surprises

Under DDP, an Incoterm that defines shipping responsibility, the sender pays all duties, taxes, and VAT upfront, and the package arrives ready for delivery with nothing owed. This is the smoother experience for your recipient — no unexpected bill, no hold at the door.

DDP is worth it when:

  • You're shipping to a customer and want a frictionless delivery experience
  • You want to avoid the recipient refusing the package over unexpected charges
  • You're shipping regularly to the same country and can build duty costs into your pricing

Delivered Duty Unpaid (DDU): Risks of Letting the Recipient Pay

Under DDU, the recipient is responsible for paying duties and taxes before the package is released — often collected by the carrier at the door or held at a local facility until paid.

The risk: if the recipient wasn't expecting a bill, they may delay payment, refuse the package, or simply not realize action is required — all of which extend the hold. DDU can also come with a brokerage fee tacked on by the carrier for handling the collection.

How to Estimate Duties and VAT Before You Ship

Before you ship, use an import tax calculator or your carrier's duty estimation tool to get a realistic number based on the destination country, product category, and declared value. This lets you:

  • Decide whether DDP or DDU makes more sense for that shipment
  • Warn your recipient what to expect if they're paying
  • Avoid pricing your product without accounting for the landed cost

How to Choose the Right Carrier and Service for International Shipping

Not all carriers handle customs the same way, and the right choice depends on what you're shipping and how often.

USPS vs. UPS vs. FedEx vs. DHL for Customs Handling

  • USPS Priority Mail International: Cost-effective for smaller personal shipments, uses the simplified CN22/CN23 declaration system, but offers less proactive customs support if something goes wrong.
  • UPS and FedEx: Strong customs brokerage built into their international services, better tracking visibility during clearance, and more consistent handling of commercial invoices — generally a better fit for business shipments.
  • DHL: Particularly strong in international and cross-border shipping infrastructure, with broad customs expertise across many countries, often a solid choice for shipments to less commonly served regions.

The right pick depends on your shipment's value, destination, and how much hands-on customs support you want built into the price.

When a Customs Broker Is Worth It (and When It Isn't)

A customs broker is a licensed professional who handles classification, documentation, and duty payment on your behalf. For most personal or low-value shipments, your carrier's built-in brokerage is enough.

A dedicated customs broker becomes worth the cost when:

  • You're shipping high-value or commercial freight regularly
  • Your product category has complex regulatory requirements
  • You're shipping to a country with unfamiliar or strict import/export compliance rules
  • A previous shipment was held or penalized for documentation errors

Why Using a Shipping Store Can Prevent Costly Mistakes

This is where a lot of people overcomplicate — or under-prepare for — international shipping. A shipping store that handles this daily will catch the mistakes above before your package ever leaves the counter: verifying your HS code, making sure your commercial invoice and customs form match, confirming whether your item is restricted at the destination, and helping you decide between DDP and DDU based on what you're sending.

For a one-off international shipment, that guidance is often worth more than the cost of the service itself — it's the difference between a package that clears customs in two days and one that sits for two weeks.

Country-Specific Rules You Can't Ignore

Import Restrictions by Country (Quick-Reference Approach)

Rather than memorizing rules for every country, build a habit: before shipping anything unfamiliar internationally, check the destination country's official customs or postal authority website for restricted and prohibited items specific to that item category. Food, plant material, cosmetics, batteries, and anything with liquid or aerosol components are the most frequently restricted.

Holiday and Peak-Season Customs Slowdowns

Customs offices, like any government agency, slow down or close entirely around national holidays. Shipping right before a destination country's major holidays, or during global peak season, adds processing delays that have nothing to do with your paperwork. Build in a few extra buffer days around these windows, and avoid shipping right before extended weekends when possible.

Shipping to the EU, UK, Canada, and Australia — Key Differences

  • EU: VAT applies to nearly all imports, and post-Brexit rules mean UK-to-EU shipments now require full customs documentation that wasn't previously necessary.
  • UK: VAT and duties are calculated based on declared value, and rules of origin paperwork may be required to access reduced rates under specific trade agreements.
  • Canada: Duties and taxes depend on the province of destination as well as the product category — and low-value shipments may qualify for simplified clearance.
  • Australia: Strict biosecurity rules affect anything organic, food-related, or wood-based, in addition to standard duty and GST calculations.

How to Avoid Extra Fees Beyond Duties

Brokerage/Handling Fees Carriers Add On

Even when duties are low, carriers often charge a separate brokerage fee for handling customs clearance on your behalf — particularly under DDU. This fee is set by the carrier, not customs, and it can catch recipients off guard if they weren't told to expect it.

Storage Fees for Delayed Packages

If a package is held at customs or a carrier facility for an extended period, storage fees can start accruing — another reason to resolve documentation issues quickly once a hold happens, rather than letting the shipment sit.

Packaging and Labeling Mistakes That Trigger Extra Charges

Incorrect weight or dimension labeling, missing customs paperwork attached to the outside of the package, or unclear labeling can all lead to reweighing charges, handling delays, or additional fees added after the fact. Confirming your box is labeled correctly before drop-off avoids all of it.

What to Do If Your Package Is Already Stuck in Customs

How to Track Down the Hold Reason

Start with your tracking number through the carrier's website — most provide a status code or brief explanation for the hold. If it's not clear, contact the carrier directly; they can often tell you whether it's a random inspection, a documentation issue, or an unpaid duty.

Who to Contact (Carrier vs. Customs Agency)

For most delays, your carrier is the right first call — they interface directly with customs on your behalf and can tell you what's needed. Only if the carrier can't resolve it, or advises you to, should you contact the destination country's customs agency directly.

How Long Customs Holds Typically Last

A routine inspection usually resolves within one to three business days. A flagged shipment with a documentation issue can take a week or more, especially if it requires you to submit corrected paperwork. There's no universal timeline — it depends on the country, the issue, and how quickly it's addressed once identified.

Pre-Shipping Checklist to Avoid Customs Delays

  • Confirm the correct HS code for every item
  • Check the destination country's prohibited and restricted items list
  • Match values and descriptions across your invoice, packing list, and customs form
  • Decide between DDP and DDU based on your recipient and shipment type
  • Estimate duties and VAT before shipping to avoid pricing surprises
  • Confirm whether a certificate of origin is required
  • Choose a carrier suited to your shipment's value and destination
  • Build in buffer time around holidays or peak season
  • Double-check labeling, weight, and dimensions before drop-off

The Bottom Line

Customs delays aren't random bad luck — they're almost always the result of a documentation gap, a misclassified item, or an unclear payment plan for duties and taxes. Get the HS code right, make sure your paperwork matches across every document, decide upfront who's paying the duties, and check the destination country's restrictions before you pack the box.

Handle those four things well, and your package has every chance of clearing customs on the first pass — no surprise fees, no mystery hold, no anxious tracking-page refreshing.

Frequently Asked Questions

Does customs open every package?

No. Customs typically reviews the paperwork and may scan the package first. Physical inspection usually only happens if something is damaged, inconsistent, or specifically selected for review.

How long can a package be held in customs?

There's no fixed limit that applies everywhere — it depends on the country and the reason for the hold. Routine holds often clear in a few days; documentation issues can take longer until resolved.

Why was I charged extra for an international package?

Extra charges usually come from unpaid duties and taxes, a carrier brokerage fee for handling clearance, or storage fees from an extended hold — sometimes a combination of all three.

How do I know if my item is restricted in another country?

Check the destination country's official customs or postal authority website for its current restricted and prohibited items list before you ship, since rules vary significantly by country and product type.

Can I refuse to pay customs fees on a package?

Yes, but refusing typically means the package is returned to the sender or destroyed, and in some cases the original shipping cost isn't refunded.

What happens if I don't pay customs duties?

The package will not be released for delivery. After a set holding period — which varies by country and carrier — it's typically returned to sender or disposed of.

Is it cheaper to ship DDP or DDU?

Neither is inherently cheaper — DDP moves the duty cost to the sender upfront, while DDU shifts it to the recipient at delivery. The better choice depends on who you want to absorb the cost and how much you value a smooth delivery experience for the recipient.