Unzipping is only the first step
A ZIP is an archive that can hold several files and folders. To prepare the invoices for your accountant, first extract the individual documents. Then open every PDF that should be an invoice and compare its contents with what you expected to receive. Successful extraction alone does not tell you whether every invoice is readable or whether any are missing.
Use the steps below for an expected attachment from a known supplier. If the message is unexpected, looks suspicious or triggers a security warning, check that the supplier sent it using contact details you already have. Do not run an unexpected application or turn off your computer’s protection to get to an invoice.
Source for this section: Apple: protecting your Mac from harmful apps
Save the ZIP and extract its contents to a separate folder
Create a working folder on your computer for this batch of documents and save the original ZIP there. Keep both the email and the archive so you can check what the supplier sent later. Work with the extracted files separately; there is no need to upload invoices to a random online extraction service.
On Windows, find the saved ZIP in File Explorer, right-click it and choose the option to extract all its contents. Select a separate destination folder and follow the instructions shown. Microsoft describes this procedure for Windows 10 and 11; the exact menu wording may vary with the system language or the program you use.
On a Mac, double-click the saved ZIP in Finder. Apple’s guide says the extracted contents appear in the same folder as the archive. Look there for the individual documents. If extraction fails or asks for a password, go to the archive troubleshooting section below.
Source for this section: Microsoft: extracting ZIP files on Windows and encrypted archive limitations in Windows 11 24H2 · Apple: extracting a ZIP on Mac and troubleshooting
Three PDFs and a note do not make four invoices
In this fictional example, the supplier says in the email that they are sending three invoices for the agreed orders. Extracting supplier-documents.zip produces the files below. This illustrates a possible folder layout; these are not real documents.
The path invoices/2026-09/invoice-101.pdf means the PDF is in the 2026-09 folder inside the invoices folder. Open the folders in turn to reach the files. Their names help you find your way, but you need to open each file to know which invoice it actually contains.
| Path inside the archive | What to look for | What to do with it |
|---|---|---|
| invoices/2026-09/invoice-101.pdf | The first expected PDF | Open every page and compare the details with the relevant purchase. |
| invoices/2026-09/invoice-102.pdf | Another expected PDF | Check it separately. Opening the previous file tells you nothing about this one. |
| invoices/2026-09/invoice-103.pdf | The third expected PDF | Read it and check that it is the remaining promised invoice, rather than another copy of an earlier one. |
| information/readme.txt | An accompanying text note in this example | Do not count it as a fourth invoice or automatically include it with the PDFs for your accountant. |
Open each PDF and match it to the expected documents
Find the files that should be invoices in the extracted contents. Open each PDF, go through every page and check that it is readable. Then compare the supplier, customer and known invoice or order number with the purchase you are dealing with. Do not take the invoice number from the filename alone.
In the example, you expect three invoices because the supplier said so in the email. But three files with a PDF extension could contain two copies of the same document and one different document. Compare each document with the list in the email or the agreed orders. If you do not know exactly what you should have received, ask the supplier for a list; the file count alone cannot confirm that everything is there.
If the ZIP extracted successfully but a PDF will not open, follow the guide below. An opening error does not prove the document is damaged. The PDF password may differ from the archive password.
The invoice arrived, but the PDF will not open. What should you send your accountant? →
If you find another ZIP inside instead of the expected PDF, ask the supplier whether it belongs in the batch and what it contains. A nested folder like the one in the table is different from another compressed archive. Do not automatically include an unclear item among the invoices you have checked.
When the ZIP asks for a password or will not extract
If you are asked for a password, check the supplier’s instructions. If you have none, use a known contact to ask how to access the archive. This means the password for the file, not the login details for your email, bank or customer account.
Even the correct password may not be enough if the tool you use does not support that type of protection. For example, Microsoft states that the built-in archive features in Windows 11 version 24H2 do not support encrypted archives. In that situation, agree a supported way for the supplier to send the documents, such as individual PDFs through an agreed channel.
For another error, note the exact message and whether it occurred during the download or when extracting the archive. If there is no security block, you can try downloading the expected attachment once more from the original email. Also check that you have enough free space for the extracted contents; Apple recommends this when troubleshooting. An error message alone does not necessarily prove that the archive is damaged.
If you still cannot extract the archive, ask the supplier to put the same documents in a new archive or send them as separate PDFs. Use the template below for an extraction error. If you simply do not have the password, just ask for access instructions.
Fill in the details you know and describe only steps you have actually taken. Omit the final sentence asking for a list if you already know which documents the batch should contain.
Select the text, copy it into an email and fill in the details in square brackets.
Source for this section: Microsoft: extracting ZIP files on Windows and encrypted archive limitations in Windows 11 24H2 · Apple: extracting a ZIP on Mac and troubleshooting
Send the checked files and explain what is missing
After checking the documents, select only those included in the agreed handover and send them through the agreed channel — for example, as attachments or in a shared folder. Keep filenames that let you identify the files later. Do not automatically send everything you extracted, including accompanying notes and unrelated documents.
If anything is missing, say so clearly. If the third invoice were missing from the example batch, your covering message could read: “I’m sending two invoices from the batch sent by [supplier]. The third invoice, for order [known number], is missing from the ZIP. I’m still arranging to get it.” If you have already asked the supplier for it, add the date of your request. Extracting a ZIP is not a reason to mark the batch as complete.
If you send documents via a link or protect them with a password, check with your accountant that they can access them. A screenshot of one page does not replace the complete document you agreed to send. Readable files alone do not establish that the invoices are correct or suitable for accounting purposes.
You now know which invoices are ready to send and which are still missing or will not open. Your accountant receives the checked files and a clear account of what remains unresolved. For a more detailed document handover checklist, see the related reading.