Sending invoices by email: professional, clear and compliant

The invoice is ready – but the email around it helps decide how quickly and smoothly it gets paid. A poorly written invoice email disappears into inbox chaos; a good one is processed within minutes. Here is how to send invoices like a professional.

The basic rule: PDF as attachment

Send the invoice as a PDF attachment – not as an image inside the message and not as a Word or Excel file. PDF is the standard format for invoices: unalterable, renders everywhere and is archived without problems by accounting systems. The email itself carries the friendly accompanying message – the invoice remains its own PDF document.

One point not to forget: since the introduction of the QR bill, the payment part with the Swiss QR Code belongs on the PDF. Invoices without a QR payment part force clients to type manually – and those are exactly the invoices that sit longest. With the QR invoice generator you create the complete PDF including payment part in under a minute.

File names with a system

The file name is faster than any search mask. Proven convention:

Invoice_2026-041_AcmeLtd.pdf

That is: the word "Invoice", the invoice number, the client name. This way you and your client find the invoice months later at a glance. Our article on numbering invoices correctly covers a clean system.

Anatomy of a good invoice email

Short, clear, friendly – a good invoice email looks like this:

• Subject: "Invoice 2026-041 – [your name/company]" – the number instead of flowers.
• Salutation: as you usually communicate with this client.
• Key sentence: "Please find attached invoice 2026-041 for CHF 2,000 with 30-day terms (due 14 September 2026)." Amount and due date directly in the email – this answers the most common questions before they are asked.
• Payment pointer: "All payment details are in the QR payment part of the invoice."
• Sign-off and signature with your complete details.

Avoid multi-page emails, marketing phrasing and above all: do not attach other documents (quote, T&Cs) unless they belong to the invoice – it confuses the client's accounts payable and slows down approval.

Large clients, administrations and eBill

With large corporations and public administrations the rule is: incoming invoices often must be delivered electronically – via eBill, as XML files or through a supplier portal. Since 2025 the Swiss public sector has been requiring electronic invoicing step by step; many administrations no longer accept PDFs at all, only structured formats (ZUGFeRD/XRechnung via eBill). Before invoicing an administration, briefly ask which format they want – it saves you returns and discussions.

For small and medium businesses, the PDF with QR payment part remains the daily reality: scan, confirm, paid.

Do not forget archiving

Sent invoice PDFs belong in a clean archive – ideally sorted by year and number, with cloud backup. The retention period for business records in Switzerland is 10 years (GeBüV); you must be able to produce invoices at any time, including in debt enforcement or a tax audit. Cloud folders meet the requirements as long as the documents are archived unalterably. rechnungslösungen.ch covers the topic in depth (in German): writing and keeping invoices in Switzerland.

Checklist before hitting send

• PDF attached, correct invoice number, QR payment part included?
• Amount and due date in the email body?
• File name following the "Invoice_Year-Number_Client.pdf" pattern?
• Correct recipient address (accounts payable instead of a personal inbox)?
• PDF archived?

Tick these five boxes and you belong to the suppliers who get paid first – because paying you causes the least effort.

Note: this article is not legal advice.