Switzerland requires businesses to keep invoices for ten years. That is the headline requirement, and most finance teams know it. What is less well understood is what "keeping" actually means — which formats are legally acceptable, what integrity requirements apply, and how the rules translate into a practical archiving setup for a company that is switching to electronic invoices.
The legal basis
The primary sources are the Code of Obligations (OR Art. 958f) and the VAT Act (MWSTG) together with the VAT Ordinance. The Code of Obligations sets the ten-year retention period for accounting records, including invoices. The VAT framework adds requirements specifically relevant to input tax deductions: for a VAT deduction to hold up under audit, the corresponding invoice must be retrievable and must demonstrate that it has not been altered since it was issued.
The Federal Tax Administration (ESTV) has published guidance on electronic invoicing and archiving in its MWST-Info publications. These are worth reading if you are designing an archiving system, as they specify what the tax authority considers acceptable evidence of document integrity.
The ten-year clock
The ten-year retention period runs from the end of the financial year in which the document was created. An invoice dated 15 March 2024 must be kept until at least 31 December 2033. In practice, most companies round up and keep everything from a given year together until the full ten-year period has elapsed for the entire year, rather than tracking individual document expiry dates.
The retention requirement covers both sides of the transaction. You must keep copies of invoices you send and invoices you receive. For received invoices, what you archive is the document as you received it — not a re-created version, not a printout of data you entered into your ERP, but the original document.
What formats are acceptable
Swiss law does not mandate a specific file format for archiving electronic invoices. The requirement is that the archived document:
- Is a faithful reproduction of the original
- Can be made legible at any time during the retention period (i.e., the format will remain readable)
- Has not been altered since archiving
For PDF invoices, a plain PDF archived in the right folder satisfies the basic requirements, provided there is a reliable system for keeping it there unchanged. The issue with plain PDFs is demonstrating that they have not been modified. A file system timestamp is not strong evidence — timestamps are trivially editable.
A better approach for PDF archiving is PDF/A-3, the archiving variant of the PDF standard. PDF/A-3 files cannot contain scripts, cannot reference external content that might change, and embed all fonts. For ZUGFeRD or Factur-X hybrid invoices, PDF/A-3 is the required container format — the XML invoice data is embedded inside the PDF/A-3 file. The ZUGFeRD archiving post goes into the technical detail.
For XML invoices (PEPPOL UBL, UN/CEFACT CII), archiving the original XML file is appropriate. The question of integrity is the same as for PDFs: you need to be able to demonstrate the file has not changed. Cryptographic hash values stored at archival time, or a qualified timestamp, provide that evidence cleanly.
Demonstrating integrity: the practical options
The ESTV accepts several approaches to demonstrating that archived invoices have not been altered:
Qualified electronic signature. A qualified signature on the document at the time of archiving proves the document existed in that form at that point. This is technically robust but adds complexity to the archiving process.
Qualified timestamp. A timestamp from an accredited provider proves the document existed before a certain point in time but does not prove it has not changed since. Combined with a hash registered at archival time, it provides solid integrity evidence.
Audit trail in a document management system. If your DMS records every access and modification event with a tamper-proof log, this can serve as integrity evidence. The ESTV expects the system itself to be documented and the audit log to be verifiable.
Immutable storage. Some archiving systems and cloud storage services offer write-once, read-many (WORM) storage where files cannot be modified after writing. This is an increasingly common and practical approach for electronic invoice archives.
The most pragmatic setup for most Swiss SMEs is a document management system or cloud archive with WORM storage, where invoices are deposited at time of receipt or sending, and the system generates a hash log. This requires no cryptographic signing infrastructure while still satisfying the integrity requirement.
Received invoices vs sent invoices
The archiving process looks slightly different for each direction.
Received invoices should be archived in the format they arrived. If a supplier sent you a PDF by email, archive the PDF. If you received a PEPPOL XML invoice, archive the XML. If you received a ZUGFeRD hybrid, archive the full PDF/A-3 including the embedded XML. Do not archive only the data your ERP extracted — that is not the invoice, it is a derivative.
Sent invoices are easier in one respect: you generated them, so you have the original. The challenge is making sure the archived copy matches exactly what was sent — if your eBill service provider or PEPPOL access point applies any transformations to the document during delivery, archive the pre-transformation version and note the transformation in your records.
Physical location and accessibility
Swiss law does not require invoices to be archived on servers physically located in Switzerland. Electronic records may be stored abroad, provided they remain accessible to Swiss tax authorities on request and can be made available within a reasonable timeframe. In practice, this means your cloud archive can be hosted in EU data centres, but you should be able to produce any requested document within days, not weeks.
The archive must be searchable. Being able to retrieve a specific invoice by invoice number, supplier name, date, or amount is expected — not just having everything stored somewhere in a folder that technically satisfies the file retention requirement but requires hours of manual searching to navigate.
The link to VAT audits
The reason archiving requirements are taken seriously in Switzerland is that VAT audits happen, and the ESTV does request specific invoices. An audit typically covers a two or three year sample period. If an auditor asks for the invoice supporting a specific input tax deduction and you cannot produce it — because it was stored on a laptop that was replaced, or in a system whose login credentials no longer work, or in a format that requires software you no longer have — the deduction is at risk.
Building an archiving process that is durable for ten years means thinking about format longevity (PDF/A-3 and plain XML are both safe bets), system continuity (what happens when you change ERP?), and access controls (who can retrieve archived invoices, and is there an audit log of retrievals?). Getting this right once, at the point of implementing e-invoicing, is far less work than trying to reconstruct it years later when a gap is discovered.