Switzerland Self-Employed — Steuererklärung & AHV Filing

Establish the taxpayer's canton and Gemeinde of residence as at 31 December, confirm permit status (Swiss citizen, C/B permit, or Quellensteuer regime), and identify church membership. Because Steuerfuss multipliers vary enormously between municipalities — Zurich city ~230% vs Wollerau (SZ) ~90% of the Grundtarif — these facts must be locked down before any computation begins. Also confirm the tax year and whether any mid-year cantonal move occurred.

Gather all bank statements (UBS, ZKB, Raiffeisen, PostFinance, BCGE, BCV, etc.) and classify every transaction as gross self-employment income, deductible Geschäftsaufwand, or an excluded item. Flag QR-Rechnung receipts, TWINT income, and Stripe/PayPal payouts (which require grossing up for platform fees). Identify all Geschäftsaufwand lines — office rent, telecoms (Swisscom/Sunrise/Salt), software (Adobe/Microsoft 365), travel (SBB/Swiss), Treuhänder fees — and exclude internal transfers (Eigene Übertragung) and tax payments (Steueramt, Eidg. Steuerverwaltung).

Compute AHV/IV/EO contributions due on net self-employment income. The combined rate is 10.0% on net earnings above the annual minimum threshold (CHF 10,100 for 2025; a declining scale applies below). Confirm whether the taxpayer has already paid provisional AHV instalments via their Ausgleichskasse and reconcile against the final figure. AHV/IV/EO contributions are fully deductible at both federal and cantonal level and must be entered before the taxable income figure is finalised.

Determine whether the taxpayer participates in a Pensionskasse (BVG / Pillar 2) and calculate the Säule 3a maximum deductible contribution. For 2025: CHF 7,258 with BVG, or 20% of net earned income up to CHF 36,288 without BVG — the higher limit is the single most powerful deduction available to the self-employed. Check if the taxpayer has already contributed and, if not, recommend topping up before 31 December. Also identify any voluntary Einkauf (buy-in) into an existing Pensionskasse.

Assemble the federal taxable income figure under DBG (SR 642.11) by deducting AHV/IV/EO, BVG, Säule 3a, Kinderabzug (CHF 6,700 per child), and Versicherungsabzug (CHF 1,800 single / CHF 3,600 married) from net self-employment income. Apply the Grundtarif (single) or Verheiratetentarif (married) from the official ESTV tariff table. Do not compute federal tax manually — use the ESTV calculator at swisstaxcalculator.estv.admin.ch. The federal maximum effective rate is 11.5%.

Compute cantonal (Staatssteuer/Kantonssteuer) and communal (Gemeindesteuer) tax using the canton-specific base tariff and current-year Steuerfuss multipliers. Note that cantonal deductions — particularly Kinderabzug and Versicherungsabzug — often differ from federal amounts; verify with the cantonal Steuerverwaltung. Apply the three-level formula: Einfache Steuer × kantonaler Steuerfuss + Einfache Steuer × Gemeindesteuerfuss + (if applicable) Kirchensteuer. For Basel-Stadt (direct tariff) and Geneva (centimes additionnels) use canton-specific calculators. Flag inter-cantonal Steuerausscheidung if the taxpayer has business activity or real property in more than one canton.

Reconcile the computed tax liability against provisional Akontozahlungen already made during the year. If the final tax exceeds provisional payments, a top-up payment must be made to avoid Verzugszins (arrears interest, typically 3-5%). If overpaid, a Vergutungszins (credit interest) applies but is low (~0-1%). File the completed Steuererklärung via the cantonal portal before the deadline (standard: 31 March; Ticino: 30 April). Submit a Fristerstreckungsgesuch (extension request) online if more time is needed — extensions to 30 September or 30 November are routinely granted.