Two criteria decide whether a Luxembourg accounting relationship works, and only the first is objective. Confirm the provider is authorised to do the work, then confirm the engagement letter names every filing and the statutory date that filing falls on.
Authorisation takes about five minutes to check, because either the ministerial permit number or the two-dimensional barcode has to appear on a permit holder's own commercial paperwork. The engagement letter decides everything else: scope, named person, what happens the day you leave. Founders rarely ask to read one before signing.
Start with the criterion you can verify
Both Luxembourg accounting titles sit inside the business-permit regime. The liberal professions guichet lists as requiring a business permit are architect, interior architect, landscape architect or landscape engineer, construction engineer, independent engineer in a discipline other than construction, surveyor, town and country planner, chartered accountant, accountant and patent attorney. Behind each accounting title sits its own entry requirement.
| Title | Qualification | Practice required |
|---|---|---|
| Accountant (comptable) | a technical secondary school graduation diploma (diplôme de fin d'études secondaires techniques ou de technicien) in the administrative and commercial division or equivalent | 3 years, at least one of them spent with an accountant, chartered accountant or auditor legally established in Luxembourg |
| Chartered accountant (expert-comptable) | a bachelor's degree in economics, finance, management, business law or equivalent | 3 years, at least one of them spent with a duly-established chartered accountant |
Both requirements are published by guichet, on its comptable and expert-comptable pages. The permit itself rests on a full set of conditions: professional integrity, professional qualification in line with the planned activity, establishment in Luxembourg, effective and permanent management of the business by the permit holder, and compliance with tax and business obligations.
You do not have to ask a candidate whether they hold one, because the 2D barcode assigned to each business permit must appear on letters, emails, websites, quotations, invoices and the shop front of every point of sale, as well as on the signs that must be installed at all construction sites.
A provider whose website, quotes and invoices carry no permit identifier is either not authorised or not observing its own display duty. Both answers are worth having before you sign anything. For the corporate side, an electronic extract on the provider's own company from the Trade and Companies Register costs €10.43 before VAT.
Audit is a separate appointment and a different professional. Where it applies, annual accounts must be audited by one or more réviseurs d'entreprises agréés appointed by the general meeting. It rarely applies at this size, because companies that stay within the article 35 small-company limits are exempt from appointing a réviseur d'entreprises agréé, so the audit is triggered by exceeding two of those three criteria.
Those article 35 limits are a balance sheet of €7,500,000, net turnover of €15,000,000 and 50 staff, and crossing the limits of two of the three criteria only changes a company's size class if it happens at two consecutive balance-sheet dates.
What the engagement is accountable for, and by when
"We handle everything" is not scope. Scope is a list of deliverables with dates on them, and for a small operating company that list fits in a table. Most engagement letters leave out the third column, which is the one that decides whether the dates are met.
| Deliverable | Statutory deadline | What has to reach the provider first |
|---|---|---|
| VAT return (monthly and quarterly filers) | monthly / quarterly returns due before the 15th of the month following the period, filed electronically via eCDF | the period's sales and purchase invoices, plus bank statements that reconcile to them |
| Annual accounts approved by the shareholders | within 6 months of the financial year-end | the closing file — stock, accruals, loan balances, anything not visible in the bank |
| Annual accounts filed with the RCS | within 1 month of approval, so at the outside 7 months after year-end | the signed shareholder decision approving them |
| Corporate tax return | 31 December of the year following the tax year | a LuxTrust product (private or pro) is required both to use MyGuichet and to sign the return |
| Employee entry declaration to the CCSS | within 8 days | the start date, declared before it happens rather than after |
Each date comes from the page that sets it: the VAT deadline from guichet's déclaration de TVA, the two annual-accounts legs from Dépôt des comptes annuels au RCS, and the tax-return date from the ACD's délais de dépôt.
Two details are worth pinning down at the first meeting. Your VAT rhythm follows turnover: annual filing can suffice below €112,000 of annual VAT-exclusive turnover, and monthly filing applies above €620,000. A quote priced on quarterly work therefore changes shape as you grow.
The second detail is that the corporate return is not paper. E-filing is mandatory via MyGuichet.lu since tax year 2017 for resident capital companies, including the s.à r.l. and the s.à r.l.-S, and what gets filed is a single return (modèle 500) covering corporate income tax, municipal business tax and net wealth tax. Whoever files it needs credentials that belong to your company, which is a conversation to have before the filing month rather than during it.
What "we handle everything" leaves undefined
Scope gaps are not usually dishonest. They are the space between what the provider assumed and what you assumed, and they surface in the month the thing is due.
| Scope tier | What the letter should name | What stays the company's obligation unless the letter transfers it |
|---|---|---|
| Bookkeeping only | posting, ledger, VAT preparation | filing the VAT return, producing the annual accounts, the tax return |
| Full statutory compliance | the above, plus the annual accounts, the RCS filing and the corporate tax return | RBE declarations, RCS filings when a manager changes, the business-permit file |
| Plus payroll | CCSS employer registration and monthly declarations, entry and exit declarations | the ADEM vacancy declaration and the employment contract itself |
| Plus registered office | domiciliation and mail handling | a legally reserved activity (see below) |
Three of those rows merit a sentence each. Beneficial-owner changes go to the RBE within 1 month, and the clock is not the one people assume: the month runs from the moment the entity became aware, or should have become aware, of the event making the entry or its amendment necessary — not from the date of the event itself.
On the payroll line, every employer wishing to hire staff must declare the vacant post to ADEM, and that declaration is due before the job offer is published.
The employment contract itself is due at the latest at the moment the employee enters service, in 2 copies. Domiciliation, finally, is not something any provider may offer. It is reserved by law to credit institutions, other financial-sector and insurance-sector professionals, list I lawyers, list IV European lawyers, réviseurs d'entreprises, réviseurs d'entreprises agréés and experts-comptables. A comptable without the expert-comptable title is not on that list, which tests whether a bundled "registered office included" offer is real.
What a missed deadline actually costs, and who it lands on
A late corporate return carries a supplement of up to 10% of the tax assessed, and unpaid tax runs at 0.6% a month from its due date. Both figures are published by the ACD. Late CCSS entry or exit declarations draw €50 per month of delay, applying only beyond a 30-day tolerance and capped at €2,500. A missed RBE update exposes the entity to a €40 daily administrative penalty.
None of that is billed to the fiduciaire. It is billed to the company, and the exposure is not only money.
Professional integrity is one of the permit conditions above, and the acts that break it include failing, on at least two occasions during the last three financial years, to meet the filing and publication obligations under the Trade and Companies Register law, 2 financial years of unfiled tax returns inside a three-year period, and persistent failure to register in the Register of Beneficial Owners over 6 months.
Filing you outsourced still attaches to your own permit, which is the argument for named deliverables and named dates.
Why the same company gets different quotes
Providers price on volume and on mess, and only one of those is fixed. Volume is transaction count and headcount. Mess is everything you control: mixed personal expenses, missing receipts, a shoebox delivered in January covering the previous twelve months. The habits in our bookkeeping guide are the habits that keep an engagement cheap to run. A file that arrives monthly and reconciles is a different product from one that has to be reconstructed.
Be wary of a quote in either direction that you cannot map to the deliverables table above. A price detached from a stated volume assumption meets reality inside a year, as surcharges or as neglect. Ask for the assumption in writing: transactions per month, employees, VAT rhythm. Then both sides can see the month it stops being true.
The questions that separate providers
- Who works on my file? A named person, or a rotating pool. Continuity is worth paying for, and it is the first thing to disappear when a firm is stretched.
- Show me the permit identifier. Any authorised provider can point at it on their own invoice or site, because they are already required to display it.
- Which of the deliverables above are yours, and by which internal date? The statutory date is the legal outer edge; the internal date is what actually gets met. A provider who plans the close in autumn beats one who discovers it in the filing month.
- What software, and can I export? Your records have to be producible by you, whatever happens to the relationship.
- What happens on the way out? Agree the handover format while everyone is still friendly. It is the clause founders skip most often.
Red flags
Chronic slowness before you sign — it does not improve after. Reluctance to put scope in writing. Books that live only in their system with no export path. Any hint of flexibility about documentation, which is not pragmatism, because the retention rules land on you rather than on the provider. Accounting records must be kept for 10 years, in Luxembourg, electronically or on paper, and invoices issued and received for 10 years from the issue date.
Common questions
When should a company engage a fiduciaire?
Before the first statutory deadline lands, not after. The earliest hard dates for a new company are the VAT registration window and, if you hire, the CCSS declarations within 8 days. The first annual accounts follow within 6 months of the first year-end, which is closer than it sounds when that year-end arrives a few months after incorporation.
Can a foreign accountant keep my Luxembourg books?
The rule the question really turns on is about the records, not the person. They must be kept for 10 years in Luxembourg, electronically or on paper, per guichet's obligations comptables. Filing is the second constraint.
E-filing is mandatory via MyGuichet.lu since tax year 2017 for resident capital companies, including the s.à r.l. and the s.à r.l.-S, and a LuxTrust product (private or pro) is required both to use MyGuichet and to sign the return. A provider outside the country runs into both, and the practical answer is usually a local provider for the filings whatever else you arrange.
What should a handover file contain?
Enough for you to meet the retention and filing obligations without them: the ledgers, the trial balance and closing entries for every open year, the invoices you are required to keep, the payroll history, and an export in a format another provider can import. Fix that list in the engagement letter, because the obligation to produce the records is the company's, not the departing provider's. Files change hands at year-end as a matter of routine.