Filing your taxes at the last minute: a survival guide

Last-minute tax return in Luxembourg? Here's how to survive the 31 December deadline and maximise your deductions with taxx.lu.

The 31st of December is creeping up, and you still haven't done your tax return? Don't panic! Here's how to avoid the stress and make the most of your Luxembourg tax return, even at the eleventh hour.

Why you shouldn't wait (and what happens if you do anyway)

Let's be honest: filling in your tax return isn't exactly top of anyone's to-do list. But in Luxembourg, the December 31 deadline is set in stone. Miss it, and you could face fines of up to 10% of the tax you owe, plus late payment interest on top.

And here's the really annoying part: any tax refund you're owed only counts if you file on time. In other words, every day you put it off is potentially money you're leaving on the table.

Step 1: Gather your documents (express mode)

Before you dive in, take 15 minutes to pull together the essentials:

• Your annual salary certificate
• Bank statements (interest paid, bank charges)
• Proof of deductible expenses: insurance, childcare, household help, donations…
• Last year's tax return (if you have it), handy for your file number and as a reference

Got everything? Great. Missing a few things? Just work with what you have. A slightly incomplete return is better than no return at all.

Step 2: Use the right tools to save time

Filling in form 100 or 163 by hand? Sure, it's possible. But honestly, who has time for that in December?

With taxx.lu, you can:

• Automatically import your tax certificates and pre-fill your data using the AutoScan app
• Pull in your personal details (name, address) from last year so you don't have to re-enter everything
• See a real-time estimate of what you'll owe or get back
• Have an expert review your return with the Plus, Premium or Platinum packages
• Book a call with the Plus or Premium package
• Discover optimisation tips after completing and paying for your return
• Get responsive support via live chat

And the best bit? No LuxTrust needed, just an email address or Google account to sign up.

Step 3: Max out your deductions (even at the last second)

Think it's too late to optimise? Think again. Some deductions can still be activated before 31 December:

Pension savings (Article 111bis)

Haven't signed up for a private pension plan yet? Now's the time. You can deduct up to €3,200 per year from your taxable income, regardless of your age. For someone in the 42% tax bracket, that's a potential saving of over €1,300.

Home savings (Bausparvertrag)

Contributions to a home savings scheme are deductible up to €672 per household member (€1,344 for those aged 18–40). A family of four could deduct up to €5,376.

Donations

Donated to a recognised charity? It's deductible from a total of €120 per year, up to 20% of your net income or €1,000,000.

Insurance premiums

Civil liability, life insurance, supplementary health insurance… all these premiums fall under the €672 cap per household member (or much more if you make a lump-sum payment on your outstanding balance insurance).

Step 4: Submit your return

Once your return is ready, you've got two options:

1. Via MyGuichet.lu (form 100 only): log in and upload your form with any attachments
2. By post: print it out, sign the last page, and send everything to your tax office (the address is on the form)

If you're using taxx.lu, the system automatically shows you the right tax office based on your postcode. Just remember: the tax office must receive your return by 31 December, so don't leave it to the very last day. The postmark doesn't count here.

One last thing: better late than never (but on time is better)

Last-minute tax returns? A time-honoured tradition. No judgement here. But next year, why not get started in spring? The forms are available from April, and your future self will thank you.

In the meantime, take a deep breath, head to taxx.lu, and let the tool guide you. Save time. Save money. Skip the stress.

Got questions? The taxx.lu team is on hand via chat to help you through. And if you want total peace of mind, our Plus and Premium packages include a human review of your return by our experts.

Start my return on taxx.lu →