Check which mailbox you're searching
In this example, you paid for hosting in April and need the invoice for Alpha Ltd. Check which email address the service is registered to. If you use several accounts in Outlook, select that mailbox and check the search scope. Results limited to one folder say nothing about an invoice stored elsewhere. Start with the supplier's name or the sender of an older invoice.
Source for this section: Microsoft: Search mail and people in Outlook on the web
Add one filter at a time
In Outlook on the web and the new Outlook, use the search options for sender, date and messages with attachments. The labels and controls vary by version. Filter by supplier first, then attachments, then date. For classic Outlook, Microsoft documents hasattachments:yes to find messages with attachments. Don't assume this is a universal instruction for every version.
For an April payment, include March too. The date filter uses the message's received date, not the invoice or payment date. If the results disappear, remove the last condition. Searching only for invoice could exclude a message whose subject says billing statement.
Source for this section: Microsoft: Find messages with attachments by Outlook versionMicrosoft: Search mail and people in Outlook on the web
An attachment isn't necessarily the right invoice
For an expected message from a known supplier, check the document: is it for Alpha Ltd, does it cover the hosting purchase, and is it the current version? One thread can contain an order, an original invoice and a correction. Save the right file with the records for that company and handover. Don't open a suspicious attachment simply because it appeared in search results.
If no attachment arrived, look elsewhere
Remove the attachment filter and read the supplier's messages. A notification may direct you to billing in your customer account. Open the service's known website and download the document there. If it's missing from the portal too, ask the supplier for a copy, identifying the purchase and customer. Tell your accountant exactly which document you're still looking for; don't present a payment confirmation as the invoice.