Top 10 Accounting Mistakes in French Construction Companies 2026

Up to date as of 14 May 2026. The five most costly accounting mistakes in French construction are: (1) reverse-charge VAT not applied on subcontracting, triggering a 40% penalty surcharge; (2) work-in-progress cut-off not performed at year-end, distorting the taxable result; (3) erroneous CIBTP DSN declaration, losing reimbursements and triggering fund reassessments; (4) retention money expensed as a loss instead of posted to receivables (account 4117); and (5) no decennial liability provision, overstating taxable income.

The accounting of a French construction or civil engineering company follows rules that have no equivalent in any other sector: retention money, reverse-charge VAT on subcontracting, job-cost accounting for work-in-progress, percentage-of-completion versus completed-contract methods, decennial liability provisions, CIBTP payroll obligations, and the construction industry's specific travel allowance regime. A general contractor, a sole-trader craftsperson, or a medium-sized civil engineering firm manipulates these mechanisms daily, and a single misclassification can trigger a tax or social security reassessment worth tens of thousands of euros. At Cabinet Hayot Expertise in Paris, we advise construction businesses of all sizes — masonry, electrical, plumbing, joinery, civil engineering, property development — and the same errors recur across the vast majority of files. This article reviews them with their legal references and operational corrections.

Three structural features of the sector create above-average exposure to errors.

The disconnect between invoicing and completion. A project spans several months or financial years: progress billings do not always match the actual revenue of the period. If the accounting cut-off is poorly handled, the taxable result is incorrect in one direction or another.

The subcontracting chain. As soon as a subcontractor is involved, VAT is no longer collected by the service provider but reverse-charged by the principal contractor. This mechanism, laid down in Article 283 nonies of the French Tax Code (CGI), is one of the most common sources of reassessment in construction tax audits.

Sector-specific social obligations. The CIBTP paid-leave fund, bad-weather allowances, and the construction industry's grand-déplacement (extended travel) scheme: each omission or incorrect classification creates a latent liability with URSSAF or the professional funds.

Mistake 1: Retention money expensed instead of posted to a receivable account#

Retention money represents 5% of progress billing amounts, withheld by the project owner for one year after completion to cover potential defects — Article R2191-24 of the French Public Procurement Code (Code de la commande publique). From the construction company's perspective, this amount is not lost: it remains a receivable from the client until released or replaced by a bank guarantee.

The frequent error: deducting retention money as an expense — reducing reported revenue or posting it to a cost account — or simply not recording it separately. Retention must be recorded in account 4117 "trade receivables — retention" on the asset side of the balance sheet. When the client releases the defect period, the balance is paid and account 4117 is cleared. If a bank guarantee is substituted (Article 2288 of the Civil Code), the retention is released immediately and the guarantee appears in the off-balance-sheet notes.

The consequence of misclassification: understated revenue or receivables, incorrect taxable result, and a distorted balance-sheet net position. On a 500,000 € (excl. VAT) project, the retention represents 25,000 € — not a trivial amount to lose from the balance sheet.

Mistake 2: Reverse-charge VAT on subcontracting not applied — the 40% surcharge#

Reverse-charge VAT on construction subcontracting is governed by Article 283 nonies of the CGI, introduced by the 2014 Finance Act and clarified by the BOFiP tax guidance (BOI-TVA-CHAMP-10-10-40-60). The mechanism: when a subcontractor (mason, electrician, plumber, etc.) works for a VAT-registered principal contractor, it is the principal contractor who accounts for VAT — not the subcontractor. The subcontractor issues an invoice exclusive of VAT bearing the mention "autoliquidation — Article 283 nonies CGI".

The classic error occurs in both directions: (i) the subcontractor incorrectly invoices 20% VAT and the principal deducts it, creating undeclared output tax for the subcontractor and double deduction in the chain; (ii) the principal contractor forgets to declare the reverse-charged VAT on its VAT return (CA3 form, lines 02 and 20), leaving a gap between the return and the purchase invoices.

A tax reassessment is systematic on audit: recovery of undeclared VAT, increased by a 40% surcharge for wilful default under Article 1729 CGI, plus late-payment interest at 0.20% per month. On 200,000 € of annual subcontracting, this amounts to 40,000 € in VAT plus 16,000 € in penalties — a 56,000 € reassessment. Joint and several liability also applies if the subcontractor defaults (Act n° 75-1334 of 31 December 1975 on subcontracting).

The operational discipline: set up two separate purchase journals — "reverse-charged subcontracting" and "normal VAT purchases" — and configure the CA3 return so that reverse-charged amounts automatically feed lines 02 and 20.

Mistake 3: Deposits and progress billings confused in job-cost accounting#

A deposit (account 4191 or 401 depending on direction) is a financial advance made before any service is rendered, with no link to actual project progress. A progress billing is an interim invoice that records a precise completion stage — works performed to a given date, tranche, or trade package — and constitutes earned revenue.

The frequent error: recording progress billings in account 4191 "deposits received" rather than invoicing them in account 411 "trade receivables" and recognising revenue in account 706 "service revenues" or 702 "sales of finished goods". The result: understated revenue, deferred VAT, and a misstated period result.

The reverse error also exists: a principal contractor pays a mobilisation advance at the start of a project, and the construction company recognises it as revenue. The period result is then overstated.

The distinction rule: if the amount corresponds to a contractually defined completion stage (percentage, tranche, trade package), it is a progress billing to invoice. If it is paid before any start of work or without a measurable service counterpart, it is a deposit to record in a counterparty account.

Mistake 4: Poor accounting cut-off for work-in-progress at year-end#

Article L.123-12 of the French Commercial Code requires accounts to be closed at the reporting date recognising revenues earned and expenses incurred, regardless of cash flow timing. The French Chart of Accounts (PCG), Articles 622-1 to 622-7, specifies the treatment of long-term contracts: the percentage-of-completion method (recognise revenue as work progresses) or the completed-contract method (everything at handover).

The most frequent error in construction SMEs: not cutting off work-in-progress at year-end. Practical consequence: an 800,000 € (excl. VAT) project started in October and 40% complete by December represents 320,000 € in revenue to recognise. If no entry is made, the period result is understated by 320,000 € and the following year will be overstated by the same amount. The tax authorities can requalify the omission as a deliberate understatement of taxable income.

Conversely, progress billings invoiced in excess of actual completion constitute an overstatement of income with a liability for repayment or correction in the following period.

The practical method: at 31 December (or the chosen closing date), prepare a work-in-progress schedule listing, for each open project: total contract value, measured completion (%), cumulative billings, and retention withheld. Accrual entries — revenue to be invoiced (account 418) and accrued expenses (account 408) — follow from this schedule.

Mistake 5: Percentage-of-completion method misapplied versus completed-contract#

Construction SMEs may use the completed-contract method (PCG Art. 622-3): no revenue is recognised until the project is handed over. This is the default for short, simple projects. Companies that have adopted the percentage-of-completion method (PCG Art. 622-7) must recognise revenue proportionally to the actual completion rate, measured by physical progress or by costs incurred relative to total estimated costs.

The most serious consistency error: mixing the two methods across projects, or switching methods from one year to the next without a note to the accounts. The French Accounting Council requires consistent application of accounting methods (PCG Art. 120-2). A change must be disclosed in the notes with a quantified impact on results.

The most frequent calculation error under percentage-of-completion: using the billing rate (amount invoiced / total contract) as a proxy for actual completion, when the two never perfectly coincide. The completion rate must be measured independently of the invoicing schedule, or the result of each interim period is distorted.

Mistake 6: Reduced VAT rate misclassified — 5.5%, 10%, or 20%#

French construction work is subject to three VAT rates whose boundaries are a constant source of error:

• 5.5%: energy-efficiency improvement works on residential buildings completed more than two years ago, including supplies and labour inseparably linked — Article 278-0 bis A CGI. This rate applies to insulation, boiler replacement, double-glazing, subject to a client attestation (tax form, to be retained).
• 10%: improvement, conversion, fitting-out or maintenance works on residential buildings completed more than two years ago (other than works eligible for 5.5%) — Article 279-0 bis CGI.
• 20%: new construction, works on commercial premises, works on buildings less than two years old, luxury works or creation of floor space.

The most costly error: invoicing energy-renovation works at 10% when they should be at 5.5%, or invoicing new-build work at 10% instead of 20%. In the first case, the company loses 4.5 percentage points of output VAT it cannot recover from the client after the fact. In the second case, a client or tax reassessment is possible. The client attestation — certifying that the building is more than two years old, used as residential, and that the works fall within eligible categories — is mandatory and must be retained for 10 years.

Mistake 7: No provision for decennial liability#

Article 1792 of the Civil Code imposes automatic ten-year liability on builders, valid for 10 years after handover. This obligation implies a real potential liability that the French Chart of Accounts (PCG) and BOFiP guidance (BOI-BIC-PROV-30-30) permit to be provisioned once the charge is probable and estimable.

The frequent error: never constituting a decennial provision, on the grounds that decennial insurance covers the claim. Insurance cover and an accounting provision are two different things: the provision represents the probable share of future uninsured claims (excess, cap overrun, undeclared claims), and it reduces the accounting and taxable result for the period as a foreseeable charge. Its absence leads to overstated income and an inflated tax base.

The calculation method common in construction files: apply a statistical percentage of construction revenue (generally 0.5% to 1.5% depending on construction type and claims history) and record the annual charge to account 152 "provisions for guarantees given to customers". This provision is reviewed annually in light of projects delivered and still within their ten-year period.

Mistake 8: Subcontractor vetting absent — joint and several liability#

Article L.8222-1 of the French Labour Code requires the principal contractor to verify, before signing the subcontracting agreement and every 6 months thereafter, that the subcontractor fulfils its social obligations. Mandatory documents: URSSAF vigilance certificate (less than 6 months old), Kbis extract (less than 3 months old), and declaration of regular employment practices.

The financial risk is direct: if the subcontractor defaults (undeclared work, unpaid URSSAF contributions), the principal contractor is jointly and severally liable for unpaid social contributions, wages and indemnities. URSSAF can pursue the main contractor for amounts sometimes exceeding the value of the sub-contract itself.

The error we regularly see in construction files at our Paris practice: URSSAF vigilance certificates are collected at contract signature but never renewed at 6 months. On an 18-month project with 4 subcontractors, that is 6 to 8 missing certificates. The discipline: maintain a subcontractor tracking table with certificate expiry dates and block payments as expiry approaches.

Mistake 9: Erroneous construction DSN — CIBTP fund and bad-weather allowances omitted#

The Déclaration sociale nominative (DSN) of a construction company must include sector-specific flows that most general payroll software does not configure automatically:

• CIBTP paid-leave fund: construction workers do not accumulate paid leave internally. The employer pays contributions to the CIBTP fund (rate variable by regional fund, around 19% to 23% of gross wages — to be confirmed against the current CIBTP publication), and workers receive their holiday pay directly from the fund. If the DSN does not include the CIBTP fund code, or if work periods are incorrectly declared, the employee's entitlement is compromised and the company may face a fund reassessment.
• Bad-weather allowances: when a site is stopped due to severe weather (frost, snow, flooding), employees may receive allowances paid by CIBTP after advance by the employer. The DSN must include the corresponding bad-weather stoppage codes. If the employer advances the allowances without correct declaration, it cannot reclaim them from the fund.

The operational consequence: a poorly configured construction DSN generates fund rejections, contribution arrears, and employee disputes over leave entitlements. Cabinet Hayot Expertise recommends a DSN audit at onboarding for every new construction payroll file, and a semi-annual CIBTP parameterisation check with the payroll software.

Mistake 10: Grand-déplacement (extended travel) allowances misclassified or underpaid#

The construction sector benefits from a specific tax and social security regime for grand-déplacement (extended travel), which applies when an employee cannot return home at the end of the working day due to the distance of the site. URSSAF publishes annual scales distinguishing meal, accommodation, and breakfast allowances by geographic zone.

The two symmetric errors seen in construction files:

Under-reimbursement: the company pays allowances below the URSSAF scales and does not record the shortfall. The employee is financially disadvantaged, and the employer has not used the full exemption available.

Over-reimbursement: the company pays allowances exceeding the URSSAF scales without evidence of actual expenses. The excess is requalified as salary by URSSAF on audit, triggering a social contribution reassessment, additional income tax for the employee, and a minimum 10% surcharge.

The practical rule: configure travel expense records for grand-déplacement based on the URSSAF scales for the current year, document each assignment (site, dates, distance between home and site), and distinguish short-distance journeys (standard mileage allowances) from grand-déplacement (construction-specific scale). For 2026 rates, refer to the URSSAF circular published at the start of the year (2025 values applicable — confirm 2026 URSSAF publication).

Construction tax audits primarily target consistency between:

• subcontracting purchase invoices (must state "autoliquidation — Article 283 nonies CGI" and be exclusive of VAT);
• lines 02 and 20 of the CA3 VAT return (reverse-charged VAT to declare);
• account 44566 "VAT on other goods and services" in the accounts;
• subcontracting agreements and the subcontractors register (Act 75-1334).

A discrepancy between these four sources is sufficient to trigger a reassessment. Documentation to retain: signed subcontracting agreement, VAT-exclusive invoices bearing the legal mention, corresponding CA3 returns, and subcontractor URSSAF certificates.

At Cabinet Hayot Expertise, closing the accounts of a construction company is organised around a work-in-progress schedule sent by the client in advance of the year-end audit:

1. List of all projects open at the closing date.
2. For each project: contract value, measured completion (%), cumulative progress billings, retention withheld.
3. Calculation of revenue to recognise = (completion × contract value) − billings already issued.
4. Identification of over-billed projects (to reverse into deferred income, account 487).
5. Check of bank guarantees substituted for retention money (off-balance-sheet).

This schedule takes 2 to 4 hours for the client on the first occasion; thereafter around 30 minutes per close, provided the job-cost accounting has been maintained correctly during the year.

In the construction accounting missions we conduct at our Paris office, three errors account for more than 80% of the real financial exposure: reverse-charge VAT on subcontracting (mistake 2), poor work-in-progress cut-off (mistake 4), and erroneous CIBTP DSN (mistake 9). The other seven accumulate and weaken the balance sheet over time, but their individual impact is slower to materialise.

The construction sector also carries a structural cash-flow pressure — public and private payment terms, retention money, bank guarantee requirements — that makes accounting misclassifications particularly dangerous: a retention receivable expensed as a loss represents a distorted cash position that can lead to a poorly informed banking decision.

The approach Cabinet Hayot Expertise applies in Paris for construction files: (i) an onboarding diagnostic covering the four highest-risk areas — reverse-charge VAT, CIBTP, retention money, work-in-progress cut-off; (ii) a quarterly review of progress billings and active subcontractors; (iii) an annotated year-end accounts with off-balance-sheet mapping (guarantees, sureties) and a calculated decennial provision. For structural questions — legal form, corporate tax versus income tax, holding structures — see our companion articles on BTP tax regime 2026 and BTP legal structure 2026. For available sector grants and exemptions, see BTP grants, financing and exemptions 2026. For financial steering, see our BTP financial KPIs 2026. Accounting mistakes in other sectors are analysed in our articles on law firm accounting mistakes 2026 and restaurant accounting mistakes 2026. Our accounting review and bookkeeping service and our construction payroll and social service — DSN, CIBTP, grand-déplacement — are managed by our Paris 8 expert-comptable team.