
Bookkeeping for engineering firms in Erlen without the stress: how it works
Bookkeeping for engineering firms in Erlen rests on three pillars: federal law that applies across Switzerland, cantonal deadlines worth knowing, and tools that eliminate re-keying. This guide puts it all in order, fact by fact.
The Swiss legal frame for bookkeeping
In Switzerland, the duty to keep accounts stems from art. 957 ff. of the Code of Obligations. Legal entities (Sàrl, SA) and sole proprietorships with at least CHF 500,000 in revenue keep full accounts: balance sheet, income statement and notes. Below that threshold, a simplified record of income, expenses and assets is sufficient.
Art. 957a CO requires complete, truthful and systematic recording of transactions, each entry backed by a supporting document. For bookkeeping, that means in practice: no movement without a receipt, and an audit trail that can be reconstructed at any time — including during a VAT or AHV inspection.
Outsource bookkeeping or keep it in-house?
Outsourcing does not exempt you from understanding: an owner who can read the balance sheet and the income statement challenges the fiduciary better — and pays for advice, not re-keying.
Changing fiduciary is not a drama: the accounting data belongs to the company, and a clean export (entries, chart of accounts, linked documents) allows a transition at year-end. A provider who locks in a client's data says a lot about how it works.
A Swiss SME's accounting calendar
Three families of deadlines shape the year: federal (VAT within 60 days, salary declaration in January), cantonal (tax return, extensions depending on the canton, including in Erlen) and internal (closing, general meeting within six months). Mixing them up is the leading cause of delays.
Delays rarely come alone: neglected bookkeeping postpones the closing, hence the tax return, hence the recalculated instalments — and the business flies blind for months. Keeping the books current as you go is the only sustainable way to hold every cascading deadline.

A well-structured SME chart of accounts
The test of a good chart of accounts is a single question: can the owner find the margins in three clicks? If not, the chart serves the tax office but not the business — even in Erlen.
For bookkeeping, a few well-chosen analytical accounts (by activity, by site) beat a forest of sub-accounts nobody ever reads.
Erlen: what changes, what does not
Erlen (postal code 8586, canton Thurgau) applies the same federal rules as the rest of the country: what changes in Erlen are the cantonal counterparts — tax administration, compensation office, commercial register.
Federal deadlines do not move in Erlen: VAT within 60 days, salary declaration in January, 10-year record retention — postal code 8586 changes nothing about those rules, only the sender's address.
Frequently asked questions
Effective VAT method or net tax rate: how to choose?
The effective method deducts actual input VAT and files quarterly; the net tax rate method applies a flat industry rate to turnover, semi-annually, with no separate input VAT deduction. The flat rate suits low-cost structures; as investments grow, the effective method usually wins again. The choice rests on the company's own figures, in Erlen as anywhere.
How much does bookkeeping cost in Erlen?
It depends on document volume, the number of salaries and VAT complexity — no serious figure can be quoted without examining the file. Two levers cut the bill everywhere: digitised, well-filed receipts and software that prepares entries instead of having them re-keyed.
What is simplified bookkeeping and who can use it?
Sole proprietorships and partnerships under CHF 500,000 of revenue may limit themselves to recording income, expenses and assets (art. 957 para. 2 CO). Once over the threshold — or upon founding a Sàrl or an SA — full accounts with balance sheet, income statement and notes become mandatory. The CHF 500,000 threshold is assessed the same way in Erlen.
What is the difference between a limited and an ordinary audit?
The ordinary audit applies to companies exceeding, for two consecutive years, two of three thresholds: CHF 20 million balance sheet total, CHF 40 million revenue, 250 full-time positions. Others fall under the limited audit, and those with no more than ten full-time positions on annual average can opt out with all shareholders' consent. These federal thresholds do not depend on the registered seat — in Erlen as anywhere.
Also worth reading
In neighbouring municipalities
Switch to accounting that keeps itself up to date
MyFiducia.ai automates bookkeeping for businesses in Erlen: AI-read documents, posting suggestions, VAT and exports ready for your fiduciary. Try the platform or browse our other guides.
The application is operated in French.