Importing Roofing Slate? The Paperwork Is Simpler Than You Think — And One Number Is the Whole Game

Part of the Roofing Slate Guide's Buying & Importing section — the paperwork half of the import story whose transport half lives in Shipping Roofing Slate Internationally, and whose quality half lives in How to Read a Roofing Slate Test Report.

Here's the honest opening that most import guides skip: the box is the easy part; the paper is the plot. I'm the one at the Jiujiang end who assembles the pack on every container that leaves our yard, so I've seen the same small tragedy repeat for a decade: the slates are perfect, the crates are sound, the container is sealed — and a clerk in a port office holds the whole thing because the gross weight on the invoice says 27,480 kg and the packing list says 27,510. That is not a shipping problem. That is a thirty-second fix, and a week of delay if nobody catches it first.

This page is the pack, laid out the way customs actually reads it. Not by name in a textbook — by the order you'll need it, the number that keeps you honest, and the two documents nobody tells you about until they're missing. Read it once and keep it next to your first order.

What Customs Actually Asks For: the Document Set, One Folder

Forget the alphabet soup for a second. Every slate import — from a 20ft container to a partial LCL load — runs on the same five to six papers. Here they are in the order you'll handle them, and what each one does in plain English:

One quick word on the bill of lading, because it's the only one of the six with a dual life. The full mechanics — original vs telex release, how the balance payment unlocks it — live in the shipping guide, and it's worth reading alongside this page. Here, the important bit is simply that the B/L is not "a piece of paper you file." It's the title to the container. Nobody's customs or trucking moves an inch without it, and that's the rule that decides your whole timeline.

The Number Game: Why One Digit Can Hold the Whole Container

Now the part that separates a smooth import from a phone call at the port — the part I tell every buyer on their first order: the customs officer is not arguing about your slate. He is checking your numbers. And three numbers are the load-bearing ones:

• The gross weight — on the invoice, the packing list, and the B/L. One number, three documents, and it must match to the kilogram. A 30 kg drift will usually clear; a 300 kg drift will hold the box while someone explains it.
• The crate count — how many wooden crates are in the container. The packing list says 22, the B/L says 22, the invoice says 22. The day one says 23, the port calls the freight forwarder instead of the forklift.
• The batch number — the production batch that ties the crates to the test report. It's the quiet one, but it's the one that proves you got the slate the lab tested. (If you don't yet know the batch you can find it on every crate — that's what makes the pre-shipment inspection the mirror image of this page.)

The discipline is boring and it's the whole game: one number, everywhere. When the factory's packing clerk writes 27,500 and the freight forwarder's clerk types 27,410 into the B/L system, that's not corruption, that's a tired Tuesday. But it's exactly the kind of small drift that keeps a 20ft box of slate sitting on the quay for four days while documents fly back and forth. The fix isn't drama — it's that before the container seals, someone lines up the three numbers across the three papers and reads them out loud. That someone, on a large order, is exactly what a pre-shipment inspection is for: the inspector's job is to catch the drift before the seal, not after the voyage.

And here's the reverse surprise that almost nobody warns you about: the number that is "too correct" also stalls. If your invoice shows exactly 27,500 kg and your packing list shows exactly 27,500 kg — because someone typed the same figure twice — customs in some ports will flag it as "inventory". Real weights drift a little because real scales drift. The honest number is the one that was actually weighed, and it's the number that moves the fastest. Don't polish the figures; keep them true.

The Two Documents Nobody Warns You About

Every new importer remembers the invoice, the packing list and the B/L. The two that trip people up are the ones that have nothing to do with the stone — and everything to do with the box and the claim.

1. The Wood Packaging Passport (ISPM 15 / IP)

Roofing slate travels in wooden crates, and almost every country now requires those crates to prove they've been heat-treated — because untreated timber can carry pests. The proof is a mark burned into the wood: IPPC / ISPM 15, with a code for the treatment plant and the country. The crate doesn't need a certificate of its own if the mark is real and readable — the mark is the document. But if the pallets or crates are unmarked — or the timber was replaced during packing and the replacement didn't get the mark — the whole shipment can be stopped, fumigated, or sent back on your own money. That's the crate standards page's territory; here the point is: a missing stamp on the wood is a hold that no clean stone can fix. Ask your supplier the question before you order, not when the crate is at your port: "Is my packaging ISPM 15 compliant?" — and ask for a photo of the stamp.

2. The Slate's Own Passport (the Test Report)

Most countries don't demand a test report at the border. But your bank, your architect, your insurer and your customer will. The report — EN 12326 or ASTM C406, from an independent lab — is the only document that proves the slate is the grade it's sold as, and it's the evidence behind the whole product story. And here's the rule: the report is only worth paper if the batch on the report matches the batch on the crates. A beautiful S1 certificate with a batch number that doesn't appear anywhere on your shipment is a certificate for someone else's slate. That's why the batch number is one of the three numbers above, and why the test report guide is the right next page — it shows you exactly which six lines to read, and how to spot the numbers that don't add up.

When the Port Says No: The Six-Step Fix

Let's say the container has arrived and customs calls you — something's not right. Before you panic, know this: almost every hold is a desk problem, not a fraud problem, and desk problems have a sequence:

1. Ask the agent for the exact line of the flag. "Weight mismatch" is different from "missing certificate." You need the verbatim reason, not the phone call version.
2. Pull the matching documents. Line by line — the flagged number is either on all three papers or on none.
3. If the paperwork agrees but the flag says otherwise: send the set to your supplier and your forwarder with one question — "which one of these is wrong?"
4. If the documents disagree with each other: that's a data-entry drift, fixable with a correction or a letter from the exporter. The crate count or weight that's off by one is usually cleared with a corrected packing list — no drama.
5. If the wood is the problem: the ISPM mark is missing on one crate — that crate sits aside for treatment or re-export while the rest clears. Don't mix it with the cleared lot.
6. And the number one rule: never let the slate move before the issue is closed. Once the goods are off the quay, a "fix" becomes a "discrepancy" that follows the file for months.

The whole point of the list: a port hold is a paper problem, and paper problems are fixable — as long as you've kept the paper. The people who lose money aren't the ones who broke the rule. They're the ones who didn't have the evidence to fix it.

The Import File: Build It Once, Reuse It Every Year

Here's the best habit I can teach you, and it costs nothing: build a folder for every order — one per container — and put the six papers in it the day the order starts. Not on arrival. On the day you place the order.

Because here's what happens every time: the order starts with a sample approval, then a quotation, then a production run, then a pre-shipment inspection — and the paperwork that belongs to each of those moments lives in three different inboxes. On arrival day, you're assembling the file from a memory and a phone. That's how "the gross weight" becomes a mystery.

The sample approval page and the pre-shipment inspection page both carry this habit: the document trail starts at the sample, and the folder should be started the same week. The six papers live in one physical or cloud file, labelled with the order number, and the arrival-day check becomes a five-minute read of a complete file instead of a treasure hunt.

So here's your job, the day you order slate: start the folder. Write "container 1" on it. And from this moment on, every document that mentions the word "slate" in the same sentence as "order number" goes in it. When the truck backs up to your door, the paper's already complete — and the only thing left to do is open the crate and enjoy the arrival inspection that has a paper it can trust.

Frequently Asked Questions

Related Reading

• Shipping Roofing Slate Internationally — the transport half of the story: incoterms, the bill of lading and the six handovers
• Pre-Shipment Inspection Checklist — catch the number drift before the seal, not after the voyage
• How to Read a Roofing Slate Test Report — the six lines that tell you the report is real
• Roofing Slate Packaging and Crate Standards — the ISPM 15 crate and the packing list that keeps the port moving
• Roofing Slate Inspection Checklist — the arrival-day plan that trusts the paper