Luxembourg Tax Filing Guide — IIT, CIT, VAT & eFiling

Individual Income Tax (IIT) — Deadline 31 December

• Individual deadline — 31 December: Individual taxpayers must file the annual income tax return (Déclaration d'Impôt sur le Revenu) by 31 December of the following tax year. For example, the 2026 return is due by 31 December 2027.
• Filing obligation: The IIT return must be filed by all individuals with taxable income exceeding the tax-free threshold (EUR 12,438 for Class 1). The return covers: employment income, business income, rental income, investment income, and capital gains.
• eFiling — MyGuichet.lu: Returns must be filed electronically through the MyGuichet.lu portal. Paper filing is only accepted for taxpayers who are exempt from mandatory e-filing (limited circumstances).
• Joint filing: Married couples must file jointly under Class 2. The combined income is split for rate calculation.

Corporate Income Tax (CIT) — Deadline 31 May

• Company deadline — 31 May: Corporate taxpayers must file the annual CIT return (Déclaration de l'Impôt sur le Revenu des Collectivités) by 31 May of the following year.
• Extension: An extension of up to 6 months may be granted upon request (filing by 30 November). Interest may apply on late payments.
• Quarterly advance payments: Companies must make quarterly advance payments (acomptes provisionnels) based on the previous year's tax liability. Payments are due on 10 March, 10 June, 10 September, and 10 December.
• Minimum CIT: The minimum corporate tax is EUR 1,500 per year (or higher based on total assets).

VAT Filing — Monthly or Quarterly

• VAT period: VAT returns must be filed: (a) monthly — for taxpayers with annual turnover exceeding EUR 620,000, (b) quarterly — for taxpayers with turnover below EUR 620,000.
• Filing deadline: VAT returns are due by the 15th of the month following the period. Payment must be made by the same deadline.
• Annual return: All registered taxpayers must file an annual VAT summary (Déclaration annuelle de TVA) by 31 March of the following year.
• eFiling — e-TVA: VAT returns must be filed electronically through the AED's e-TVA portal, accessible via MyGuichet.lu.

Withholding Tax (RAS) — Monthly Declarations

• Monthly withholding: Employers must withhold income tax at source (retenue à la source, RAS) from employees' salaries on a monthly basis. The withholding is calculated using the progressive IIT scale.
• Monthly declaration: The employer must file a monthly withholding declaration by the 15th of the following month through the eTVA portal.
• Annual certificate: Employers must issue an annual salary certificate (Certificat de Retenue à la Source) to each employee by 31 January, summarising gross salary, deductions, and tax withheld.

eFiling — MyGuichet.lu and eTax Portals

• MyGuichet.lu: The centralised e-government portal for Luxembourg. Taxpayers can file IIT and CIT returns, view their tax account, and communicate with the ACD.
• eTax portal: The dedicated tax portal for professional taxpayers (companies, self-employed, VAT filers). Supports VAT returns, withholding declarations, and corporate tax filings.
• Mandatory eFiling: E-filing is mandatory for all companies and individual taxpayers with taxable income exceeding EUR 15,000 per year. Electronic signature (Luxtrust or similar) is required.

Tax Audit Procedures

• Tax audit — contrôle fiscal: The ACD may conduct a tax audit to verify the accuracy of tax returns and compliance with tax laws.
• Types of audits: (a) desk audit (vérification sur pièces) — review of submitted returns and documents, (b) field audit (vérification de comptabilité) — on-site review of books and records, typically covering 3 to 4 fiscal years.
• Audit process: The ACD issues an audit notice at least 8 days before the audit. Taxpayers have the right to representation and appeal rights.

Penalties — Late Filing and Late Payment

• Late filing penalty: EUR 50 to EUR 10,000 depending on the delay and the taxpayer's turnover.
• Late payment interest: 0.6% per month on the tax due, calculated from the due date to the payment date.
• Tax reassessment penalty: 10% of the additional tax if the underpayment results from negligence. 50% if from wilful misconduct or fraud.

FAQs

What happens if I miss the individual tax filing deadline?

Late filing interest of 0.6% per month applies from the original due date. The ACD may also issue a formal reminder and impose a late filing penalty. It is better to file late than not at all, as penalties for non-filing are higher.

Can I file a joint return with my spouse?

Yes, married couples must file jointly under Class 2. The joint return requires both spouses' signatures. The benefit of joint filing is income splitting, which generally results in a lower effective tax rate for couples with unequal incomes.

Do I need to file a tax return if I only have employment income?

If your employer has correctly withheld tax at source and you have no other income, you may not need to file. However, if you want to claim deductions (mortgage interest, pension contributions, donations) or if tax was over-withheld, you should file to receive a refund.

Disclaimer

This guide provides general information about Luxembourg tax filing for the 2026 tax year. Tax laws and rates may change. Always consult with a qualified Luxembourg tax advisor (conseil fiscal) or the ACD directly for advice specific to your situation. InvestmentKit does not provide tax advice.