Issuing an advance invoice before work begins: 6 pitfalls to avoid

Issuing an advance invoice before the actual work begins puts you in a tight spot: the legal requirements are the same as for a standard invoice, but the timing creates special pitfalls. Especially at project kickoff, when no service has yet been delivered, confusion arises about content, wording, and booking. The following six mistakes appear repeatedly in practice — and can be easily avoided with a little preparation.

Mistake 1: No clear link to the contract

An advance invoice that merely says "payment for project" is legally weak. If the connection to the specific contract or offer is missing, disputes become tricky — both with the customer and during a VAT audit.

What's better: Reference the quotation number, project code, or the date of the signed contract. Example: "Advance payment per quote no. 2026-047 dated 15 July 2026, web development for Mustag GmbH". This ties the invoice to a specific legal relationship.

Mistake 2: Performance description too vague or missing

Many issue an advance invoice without describing what the payment covers. Swiss VAT law requires a sufficiently specific service description even for advance payments — because the tax rate depends on the type of service to be delivered.

If you're pre-financing an interior design service, for example, you must make clear in the advance invoice that it's a service subject to the standard rate of 8.1%. A catering company collecting a deposit for an event with food and beverages must either estimate the VAT allocation in advance or clarify which rate applies. Our guide to Swiss VAT basics 2026 helps you choose the correct rate.

Mistake 3: No explicit label "advance invoice"

Without the term "advance invoice" or "deposit invoice", the document lacks semantic clarity. Accountants on the customer side won't know whether a final invoice follows or whether the amount is complete.

Mark the document clearly: in the title ("Advance Invoice No. AV-2026-012"), but also in the body text ("This amount will be deducted on the final invoice"). This prevents follow-up questions and simplifies booking on both sides.

Mistake 4: Wrong or missing invoice number

Advance invoices need their own sequential invoice number — just like any other outgoing invoice. A common mistake: the advance invoice is numbered the same as the later final invoice, or gets no number at all.

This creates chaos in accounting and can raise questions during a VAT audit. Create a separate numbering series, for example with prefix "AV" or "DEP", or integrate advance invoices into your existing sequence. What matters is continuity.

Mistake 5: QR-IBAN missing or IBAN doesn't match your bank

An advance invoice is only complete when the payment section is correct. In Switzerland, the QR-bill has been the standard since 2022. If you enter an IBAN instead of the correct QR-IBAN or omit the payment slip, you risk payment delays — especially unwelcome when the deposit is supposed to finance project planning.

Check: do you have a QR-IBAN from your bank? It differs from a regular IBAN and is required for a valid QR-bill. Our step-by-step guide to creating a Swiss QR-bill explains the entire process.

Mistake 6: Payment deadline unclear or missing

For an advance invoice before project start, the payment deadline is especially important because your project cashflow depends on it. Yet it's often omitted or simply states "30 days net" — without a date.

Be specific: "Due 22 August 2026". If appropriate, add an early payment discount, such as "2% discount if paid by 12 August 2026". This reduces default risk and makes cashflow more predictable. Make sure the deadline is realistic: if you start on day one of a three-week project, you can't set a 60-day deadline when work should begin in week two.

Checklist: advance invoice before project start

Element	Why it must be included
Label "advance invoice"	Clear distinction from final invoice
Own invoice number	Complete accounting records, VAT compliance
Reference to quotation/contract number	Legal assignment, binding nature
Concrete service description	VAT rate determination, customer communication
VAT disclosure (rate + amount)	Mandatory for VAT-liable businesses
QR-IBAN and QR-code	Payability per Swiss standard
Specific payment date	Cashflow control, basis for reminders
Note on later deduction	Transparency with customers and accountants

If you want to create advance invoices digitally and issue them directly with a QR-code, you can do this via SnapBill — the required fields are pre-filled, and the QR-code is generated automatically.

Special case: advance invoices to private individuals

Private individuals cannot claim input VAT anyway, but VAT disclosure remains relevant: your own accounting with the tax authorities is based on either the date of payment receipt (cash basis) or invoice date (accrual basis). If you declare in the wrong quarter, you risk late fees. Always issue the advance invoice in good time — ideally in the same quarter you expect the payment.

At a glance

• Always explicitly label advance invoices as such and assign your own invoice number.
• Reference the underlying quotation or contract.
• Describe the service concretely enough to justify the correct VAT rate.
• Use the QR-IBAN and a complete QR-bill payment slip.
• Set a specific payment date — not "30 days net" without a reference date.
• State that the amount will be deducted on the final invoice.