Start with the details inside the PDF
Open the renamed PDF and note the issuer, document number, issue date and amount, including the currency. Add the customer, particularly if your shared folder holds invoices for several companies. These details help you decide which attachments are worth comparing.
In the example document, the issuer is Hosting Alfa, the number is FA-1042, the issue date is 15 September 2026, the amount is CZK 1,210 and the customer is Firma Alfa. A colleague chose “09” in the filename; it tells you neither when the message arrived nor the date on the invoice.
A similar name or matching amount may point you towards the right attachment, but neither identifies it on its own. A subscription may cost the same every month, and different suppliers may use the same document number. Compare the details together. Do not infer missing information from the filename.
Ask where your colleagues got the file
Start with the person who last saved the file: “Where did you get Alfa_faktura_09.pdf, and what was it called before?” If they got it from another colleague, ask that person next. Request the specific message or location from which they downloaded the attachment. This can take you from the latest name back to the original without searching the entire mailbox.
If your colleagues do not know the source, search the mailbox where the supplier usually sends invoices. Start with the supplier’s address and an approximate delivery period. The issue date helps you choose a period, but the message may have arrived later. Try the invoice number too, if the supplier included it in the subject or email body.
For a forwarded email, distinguish your colleague’s message from the supplier’s original email. If you find only the forward, keep it and record that fact. A sender’s name in the quoted text does not mean you have the original message available.
In Gmail, search by sender and attachment
If you use Gmail, you can combine conditions in a single query. The illustrative query “from:fakturace@example.com after:2026/09/01 before:2026/10/01 filename:pdf” searches for PDF attachments from that sender during the chosen period. If you know the original name, try “filename:invoice_1042.pdf”. A name assigned later in a shared folder may not find the original message.
If nothing turns up, widen the date range or remove the sender condition. The query “in:anywhere filename:invoice_1042.pdf” includes spam and trash. Open the specific message and its attachment in the results: not every message in a matching conversation necessarily meets the query. Google’s help page listed in the sources explains these operators; other email services use different search tools.
Open the attachment and compare the whole document
Open the attachment you found beside the renamed PDF. Compare the issuer, customer, document number, date and amount, including the currency. Then check the line items, notes and every page. Otherwise, matching main details could conceal a change in a less obvious part of the document.
If you find no difference, record which email attachment you compared the file with and what you checked. The result describes that comparison; it does not confirm that the invoice is authentic. Even matching file hashes alone do not establish who actually issued it.
Keep the original attachment unchanged and record its name alongside the working name. Do not edit information inside the invoice just to standardise filenames. If the contents differ, retain both versions and ask for an explanation: the difference may indicate another document or a revision rather than a simple rename.
Save a note that helps a colleague find the source
Once you locate the attachment, save a short note beside the document or in your team’s records. Alongside the email link, include the mailbox, sender, delivery date, subject and original attachment name. Your colleague will know where to look; the link itself is useful only if they have access to the mailbox. If you also save the original message elsewhere, record that location.
Here is a completed note for our illustrative example. All names, addresses and dates are fictional:
Working file: Alfa_faktura_09.pdf. Previous working name: hosting-zari.pdf. Original attachment: invoice_1042.pdf. Document: Hosting Alfa, FA-1042, issued 15 September 2026, CZK 1,210, customer Firma Alfa.
Source: mailbox doklady@example.com; sender fakturace@example.com; delivered 16 September 2026 at 09:18; subject “Invoice FA-1042 for hosting”. The original message remains in this mailbox and contains invoice_1042.pdf.
Comparison: on 2 October 2026, Jana compared the working PDF with the original message’s attachment. She found no difference in the issuer, customer, number, date, amount, line items or any page. The names hosting-zari.pdf and Alfa_faktura_09.pdf were created by our team, not used by the supplier.
This record connects the file to the message and states who compared it and when. The next time someone asks, a colleague can go straight to the source instead of asking both people who renamed the file again.
If the source is missing or the contents differ, ask a precise question
If you cannot find the original attachment, record what you have and what is missing. For example: “Only a colleague’s forward retained; supplier’s original message not found.” Then ask the supplier to resend it. If you found different versions, ask them to explain the change. Tell your accountant which version they have already received and what you still do not know.
You can use this illustrative message when the email is missing:
Hello, we are looking for the original email for invoice FA-1042 from Hosting Alfa, issued on 15 September 2026 for CZK 1,210 to Firma Alfa. We have the PDF saved as Alfa_faktura_09.pdf, but have been unable to find the original message. Could you please resend the invoice and confirm whether you also sent a revised version under this number? Thank you.
If the files differ, add the specific difference you found to your request. The supplier will not have to start the comparison from scratch. Attach their reply to the document’s note so the explanation remains traceable even after another rename.