Invoice Date vs. Service Date: Why Both Matter on a Swiss Invoice

A Swiss invoice carries two different dates: the invoice date (when you issue it) and the service date or period (when the work was performed). They serve different legal purposes.

The invoice date

This is the date the document is issued and it anchors the invoice in your bookkeeping. For VAT purposes, the invoice date generally determines which reporting period the turnover falls into.

Under the agreed-method of VAT accounting, turnover is reported when the invoice is issued, not when the cash arrives. That makes the invoice date the decisive one for filling in your quarterly VAT return.

The invoice date also starts the clock on payment terms. If you write "30 days net", the due date is counted from the invoice date, so getting it right matters for your cash flow too.

In bookkeeping software, the invoice date is usually what determines the posting period. Issue an invoice on 31 December and it lands in that year, even if the client only pays in January.

The service date or period

The service date records when the work was actually delivered or performed. For a project billed in March for work done in January, the service period is January, not March.

This matters for your customer’s accrual accounting. They must recognise the expense in the period the service was received, so a clear service date lets them book it in the correct month or quarter.

A service period also matters in disputes. If a client questions when the obligation arose or whether a warranty period has run, the stated service date is the evidence both sides fall back on.

For recurring or long-running work, write a range rather than a single day. A period such as "January 2026" or "1–31 January 2026" is precise enough and removes ambiguity about which month the work belongs to.

How the two dates interact

The invoice date and the service date often differ, and that is fine as long as both are stated. The invoice date fixes the bookkeeping and VAT period, while the service date fixes the economic period.

For VAT, a common source of error is booking turnover into the month of the service instead of the month the invoice was issued. Under the agreed method it is the invoice date that counts, so keep the two clearly separate.

For income tax, revenue is generally recognised when the performance is rendered, which is why the service date matters for your annual accounts. A December service invoiced in January still belongs to the previous tax year.

When the two dates fall in different years, the mismatch can shift taxable income across a year boundary. State both dates explicitly so that you and your accountant can assign the turnover to the correct period without guessing.

Getting both dates right

Always print both the invoice date and the service date or period on the invoice. Leaving the service date off forces your client to guess and invites errors in their books.

Set the invoice date to the day you actually issue the document. Post-dating or back-dating an invoice to move it into a friendlier period is exactly the kind of thing an auditor will notice.

If the service date is the same as the invoice date, you can state it once or write "same as invoice date". The key is that there is never any doubt about when the work was performed.

Use software that stores the service date as a separate field rather than relying on a comment in the description. That way the two dates cannot drift apart and every invoice carries the correct pair.

• Invoice date = when the document is issued (drives the VAT period).
• Service date = when the work was performed (drives accrual).
• State both, even when they are identical.
• Never back-date or post-date an invoice.