What «tax audit» means in Switzerland
Switzerland has no single tax police: audits may come from the cantonal authority (income and wealth tax), the FTA (VAT, withholding tax, stamp duty), compensation offices (social contributions) or an appointed auditor (limited or ordinary audit). Each asks for different documents, but all rely on the same rule: the taxpayer must prove every declared figure (Art. 125 TPA).
The law requires books and supporting documents to be kept for 10 years from year-end (Art. 958f CO, Ordinance on bookkeeping). An audit on 2024 may require documents from 2015 onwards. Those who keep everything «in one folder» or scattered Excel lose days reconstructing — and the authority may estimate unfavourably (Art. 130 TPA) what is not documented.
This guide does not replace a fiduciary, but provides an operational checklist: which documents to keep ready, how to organise them and how to behave when the summons arrives. Goal: exit the audit with minimal adjustments and no avoidable surcharges.
Types of audit: who asks for what
Before preparing documents, identify which authority summoned you.
| Authority | Scope of review | Typical documents requested |
|---|---|---|
| FTA (federal) | VAT, withholding tax, stamp duty | VAT returns, VAT invoices, purchase/sales registers, FTA correspondence |
| Canton / Municipality | Income and wealth tax | Returns, financial statements, deduction receipts, material contracts |
| AVS compensation office | Worker classification, salaries, contributions | Contracts, payslips, contribution payment proof, employee vs self-employed distinction |
| Auditor / Commercial register | Correctness of accounts CO Art. 957a | General ledger, trial balance, financial statements, notes, assembly minutes |
Master checklist: 8 categories always ready
If you keep these eight categories current during the year, a surprise audit becomes manageable in days instead of weeks.
| Category | Retention | Ideal status |
|---|---|---|
| Books and financial statements | 10 years | Closed annually, exportable to PDF |
| Invoices issued and received | 10 years | Numbered, linked to payments |
| Bank statements and reconciliations | 10 years | Reconciled quarterly |
| Tax returns and filings | 10 years | Copy filed + submission receipt |
| VAT documentation (FTA) | 10 years | Aligned with quarterly returns |
| Material contracts and agreements | Contract term + 10 years | Signed, indexed by client/supplier |
| Payroll and AVS (if employees) | 10 years | Payslips + time records |
| Authority correspondence | 10 years | Dedicated folder by year and authority |
Category 1: Books and financial statements
The basis of every audit. Without coherent books, everything else is contestable.
- 1General journal (or equivalent entries) with date, text, amount, debit/credit account for every transaction in the audited period
- 2General ledger / chart of accounts with verifiable opening and closing balances
- 3Trial balance before and after year-end adjusting entries
- 4Approved balance sheet and income statement (for LLCs/Corps: assembly minutes approving them)
- 5Notes to the financial statements and management report, if required
- 6Fixed asset register with depreciation schedule and purchase documentation
Category 2: Invoices issued and received
Every income and expense line must trace to a document. The authority may sample 20–50 invoices and request payment proof.
- 1All issued invoices with sequential numbering, date, client, tax base, VAT and total (LIVA-compliant if VAT-registered)
- 2PDF or original of every received invoice with supplier, date and visible VAT amount
- 3Credit and debit notes linked to original invoices
- 4Contracts or orders supporting large amounts or recurring payments
- 5Proof of collection for issued invoices (bank statement, QR confirmation) and proof of payment for received invoices
- 6For mixed expenses (car, phone, home office): documented professional share calculation
Category 3: Bank statements and reconciliations
The bank account is the «truth» the authority compares with your accounts.
- 1Complete statements for every business account for the entire audited period (bank PDF or MT940/CSV export)
- 2Bank reconciliations signed or tracked in software (book balance = bank balance at each month-end)
- 3List of unreconciled items with written explanation
- 4Proof of every transfer between personal and business account (if any remain) with description
- 5Foreign payment documentation: exchange confirmation, invoice, customs declaration if applicable
Category 4: VAT documentation for the FTA
For VAT taxpayers, the FTA verifies that every return figure is reconstructible.
- 1Copy of every VAT return filed with FTA portal transmission receipt
- 2Purchase and sales VAT register for the period (or export from accounting software)
- 3List of invoices with input tax deducted, linkable to the return
- 4Documentation for effective or net tax rate method: comparative calculation if you changed method
- 5FTA correspondence: registration, net rate decisions, extensions or agreements
Category 5: Payroll, AVS and remuneration (if applicable)
If you have employees or collaborators, social security offices may verify in parallel.
- 1Employment or collaboration contracts with clear employee vs self-employed definition
- 2Complete payslips for every month of the audited period
- 3Attendance or hour records for hourly workers
- 4Proof of AVS/AI/IPG/BVG and mandatory insurance payments
- 5Documentation of remuneration to directors, family members or related parties
Category 6: Tax returns and taxes
The cantonal authority compares the return with accounts and prior filings.
- 1Income and wealth tax return (individual or corporate) with all schedules
- 2Copy of return filed and any assessment decision received
- 3Receipts for advance payments and final tax balance
- 4Certificates for special deductions: pillar 3a, pillar 2, debt interest, donations
- 5For LLCs/Corps: corporate return, capital participation, documented dividend distributions
Category 7: Contracts and extraordinary documents
Often requested on sample basis for «suspicious» items: rent, consulting, international transfers.
- 1Office lease or professional home office share agreement
- 2Contracts with main clients and suppliers (especially amounts > CHF 10,000)
- 3Related-party agreements: shareholders, family, group companies
- 4Documentation of extraordinary transactions: asset sales, investments, loans
- 5Correspondence with fiduciary and auditor for the audited period
Category 8: Authority correspondence
Showing timely and correct responses reduces surcharges.
- 1Every letter, invitation or questionnaire from FTA, canton or social security office
- 2Copy of responses sent with date and reference
- 3Any extensions requested and confirmations received
- 4Internal log: who handled the audit, which documents delivered and when
During the audit: 5 golden rules
How you cooperate influences the outcome as much as the documents.
1. Read the summons carefully
Verify period, years under review and competent authority. Do not deliver more than requested, but omit nothing explicitly listed.
2. Designate a single contact
Owner or fiduciary: one person responds to avoid contradictions. The contact has full access to the digital archive.
3. Do not «fix on the fly» without a trail
If you find an error, disclose it with documentation of the correction. Silent fixes during the audit may be seen as bad faith.
4. Respond within deadlines
Cooperation reduces surcharges (Art. 151 TPA). If you need more time, request an extension in writing before the deadline.
5. Keep a copy of everything you deliver
Single PDF «audit package 2024» with index: helps with follow-up audits or appeals.
Digital organisation: recommended folder structure
A standard structure avoids panic. Adapt to your software, but keep the logic:
Certified cloud archiving (Ordinance on bookkeeping, Art. 958f CO) automatically links invoice, payment and accounting entry — the checklist builds itself over time.
7 practical tips
- Run an annual «internal audit»: sample 10 invoices and verify payment and booking exist
- Do not wait for the summons to digitise: stressed scanning costs triple
- Keep archives by fiscal year, not one pile «everything since 2018»
- If you use cash, keep a cash book with every movement and receipt — the FTA watches closely
- Align tax return and accounts before filing: discrepancies trigger audits
- Give read-only access to your fiduciary before the audit for preventive review
- After the audit, archive the outcome (decision, adjustments) in folder 08_Audits
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