How to File Your Income Tax via Tax-on-web (MyMinfin)

If you have lived in Belgium for more than a few months, you likely know the specific dread that comes with receiving a digital notification from the SPF Finances. My first time, I spent three hours staring at a screen filled with Dutch terms I didn't understand, convinced I was going to be fined thousands of euros. This guide solves that confusion by breaking down every step of the Tax-on-web process for expats.

Understanding the Belgian Tax Calendar and Deadlines

One of the most confusing aspects of the Belgian system is the distinction between the "income year" and the "assessment year." In Belgium, you always file your taxes for the money you earned in the previous calendar year. For example, if you are filing in 2026, you are reporting your income from January 1 to December 31, 2025. This is officially known as the Assessment Year 2026. If you forget this, you might find yourself looking for documents that don't exist yet or worrying about a salary you haven't even received.

The deadlines are also famously strict, though they vary depending on how you file. For most residents using the online Tax-on-web portal, the deadline usually falls in mid-July. However, if you use a certified accountant (comptable or boekhouder), they often have a longer window, sometimes extending into October. It is vital to check your specific deadline on the MyMinfin portal as soon as it opens in May. Missing these dates can result in automatic taxation by the state, which is almost always higher than what you actually owe, plus administrative fines that start at 50 euros and scale up quickly.

There is also a separate category for those who are considered non-residents. If you live in Belgium but your primary economic interests or family remain abroad, or if you are here on a specific status, you might be filing a different form. You can read more about this in our guide on Filing a Non-Resident Tax Return (Impôt des Non-Résidents). The non-resident deadline typically falls later in the year, often in November, but do not count on this unless you have confirmed your status with the tax office.

Tax Year vs Assessment Year Confusion

For a newcomer, the terminology used by the SPF Finances (the Federal Public Service for Finance) can feel like a riddle. You will see "Exercice d’imposition" (Assessment Year) and "Revenus de l’année" (Income Year). Always remember that the Assessment Year is the current year you are sitting at your computer, and the Income Year is the year that just passed. This is particularly important when you are calculating your Social Security in Belgium: Employer and Employee Contributions to ensure they match your annual fiscal fiche.

If you arrived in Belgium midway through the year, your first return will be a "special" one. You only report the income earned from the date of your registration at the commune. Many expats make the mistake of trying to report their global income for the entire year on their first Belgian return, which can lead to double taxation if you aren't careful about tax treaties. Always keep your payslips (loonfiches/fiches de paie) from your previous country just in case the Belgian authorities ask for proof of tax paid elsewhere.

Specific Deadlines for Residents and Non-Residents

The Belgian government is slowly moving toward a fully digital system, and they incentivize this by giving digital filers more time. Paper forms—those big brown envelopes—are becoming rare and usually have the earliest deadlines in June. If you still receive a paper form, I highly recommend switching to the digital portal immediately. It not only saves time but also provides a "calculation" tool that gives you a preview of your refund or the amount you need to pay.

For those with complex situations, such as freelancers or those with foreign income, the deadlines are your best friend. If you feel overwhelmed as the July deadline approaches, that is the moment to contact a professional. If you are curious about how your income is actually sliced by the government before you even hit the "submit" button, you can check our breakdown of Belgian Tax Brackets 2026 (Assessment Year 2027): 25% to 50% to see where your salary falls.

Accessing the Portal: Itsme and eID Card Readers

To file your taxes via Tax-on-web, you must first access the MyMinfin portal. This is where most foreigners hit their first wall. You cannot simply create a username and password with an email address. The Belgian government requires a high level of digital security. You have two main options: using an eID card reader with your Belgian residency card and its PIN code, or using the Itsme app. In my experience, the eID card reader is a relic of the past that only leads to driver errors and frustration.

The Itsme app has become the gold standard for living in Belgium. It links your identity to your phone number and your residence permit. Once it is set up, you can log into almost every government site, including your bank and the health insurance portals, with a single fingerprint or a five-digit code. If you haven't set this up yet, it should be your number one priority. You can follow our tutorial on Itsme Authentication: How to Set Up Belgium's Vital Digital ID to get it running in minutes.

Setting Up Itsme for Tax Filing

To set up Itsme, you usually need a Belgian bank account or your eID card and a reader for the initial verification. Once the app "knows" who you are, logging into MyMinfin becomes a matter of seconds. You go to the site, choose "Log in via Itsme," enter your phone number, and then confirm the action on your phone. This eliminates the need to remember your eID PIN code, which most of us forget about three days after leaving the commune.

For expats who have just arrived and might not have their physical residence card yet, accessing Tax-on-web can be tricky. If you only have an Annex 15 or a temporary document, you may need to visit a local tax office in person to get a "token" or a temporary login. However, once you have your card, Itsme is the only way to go. It prevents the nightmare of your session timing out while you are halfway through a complex declaration, as it keeps the authentication active across your devices.

Troubleshooting the eID Card Reader

If you are a traditionalist or your phone doesn't support Itsme, you will need a USB card reader. These are sold at shops like Fnac or MediaMarkt for about 15 euros. You insert your Belgian eID card, enter your PIN, and wait for the browser to recognize the certificate. The common issue here is the "middleware" software. You must download the official eID software from the Belgian government website. If the browser says "No Certificate Found," it usually means the software isn't running in the background or your card is dirty—give the gold chip a quick wipe with a dry cloth.

Another common frustration is when your eID card has been renewed but the certificates haven't updated in the system. If you recently moved or changed status, the tax portal might still be looking for your old card details. In these cases, a quick trip to your local commune to "refresh" the card can solve the login loop. It’s these small administrative hurdles that often make expats feel like giving up, but persevere—once you are in the portal, the hard part is mostly over.

Navigating the MyMinfin Dashboard

Once you successfully log in to MyMinfin, you will be greeted by a dashboard that looks quite modern but is dense with information. Look for the tab labeled "Ma Déclaration" or "Mijn Aangifte." This is where the Tax-on-web application lives. Before you start clicking, take a moment to look at the "Documents" section. The Belgian government is quite efficient; your employers, banks, and even your mutuelle (health insurance) send your data directly to the tax office.

This means that for many people, the tax return is already 80% filled out. You aren't "writing" a return so much as you are "verifying" what the government thinks you earned. This is where the "Proposal for Simplified Declaration" (PDS) comes in. If you are a standard employee with no complex assets, you might receive a letter saying the government has already calculated everything for you. If you agree with their numbers, you don't actually have to do anything. But be careful—the government often misses deductions that could save you money.

The Proposal for Simplified Declaration (PDS)

The PDS is a double-edged sword. It feels great to see a message saying "You don't need to do anything," but I have found that the PDS rarely includes things like foreign bank accounts or specific expat deductions. If you have a Expat Tax Regime in Belgium: The New Special Tax Status (RSMI), you absolutely must check that the percentages are applied correctly. The PDS is essentially a draft. You have the right to log in, click "Modify," and add the details they missed.

Most expats find that their rental income (if they own property) or their foreign savings are missing from the PDS. If you simply ignore the PDS because it looks easy, you might be technically committing tax fraud by not declaring those foreign accounts. Always open the draft, compare it with your own records, and ensure every box is filled correctly. The time you spend verifying could be the difference between a 200-euro bill and a 1,000-euro refund.

Preparing Your Documents (Fiche de Paie)

Before you sit down to file, gather your "Fiche 281.10." This is the annual summary your employer provides. It lists your total gross salary, the tax already withheld (précompte professionnel), and your social security contributions. You will also need fiches for any other income: Fiche 281.11 for pensions, or 281.14 for unemployment benefits. Having these ready allows you to cross-reference the numbers already present in Tax-on-web.

If the numbers in the portal don't match your fiches, don't panic. Errors happen. You can manually overwrite the fields in Tax-on-web, but you should be prepared to upload a PDF of your fiche as evidence. The system allows you to attach "annexes" to your return. I always attach a digital copy of my annual salary statement just to be safe. It’s also a good idea to check if you have any Tax-Free Savings Accounts (Category A): Limits and Exemptions that could be used to offset your taxable income.

Declaring Foreign Assets and Accounts

This is the section where almost every expat gets caught out. Belgium has a "global" tax system, meaning if you are a resident, you must declare your worldwide income and assets. Even if your account in your home country only has five euros in it, it must be declared. This is done in two places: on your actual tax return (Part 1, Code 1075) and via a separate filing with the National Bank of Belgium (NBB).

If you use international fintech services, you might not even realize you have "foreign" accounts. For example, if you have a Wise account with a Belgian IBAN, you are usually safe, but many older accounts are held in the UK or elsewhere. Similarly, if you use Trade Republic for your investments, that account is technically German. Even your Binance account or other crypto platforms must be disclosed if they hold cash or act as a digital wallet. The Belgian tax office receives data from other EU countries, so if you don't declare your Wise or Trade Republic accounts, they will eventually find out.

The National Bank of Belgium (NBB) Declaration

The NBB declaration is a one-time task, though you must update it if you open new accounts. You need to provide the account number, the bank name, and the country where the account is held. This is not done within Tax-on-web; it is a separate portal. However, on your tax return, you must check a box confirming that you have declared these accounts to the NBB. If you check that box but haven't actually done the NBB filing, you are flagging yourself for an audit.

Many people find the NBB portal confusing because it asks for the "initial year" of the account. If you've had your Binance or Wise account since before you moved to Belgium, the "initial year" should be the year you became a Belgian resident. For more detailed instructions on this specific hurdle, see our guide on Declaring Foreign Bank Accounts to the Belgian National Bank (NBB). Keeping this updated ensures that your Tax-on-web filing remains "clean" and less likely to be flagged for review.

Declaring Foreign Real Estate

If you own a house or apartment outside of Belgium, you must declare it. This doesn't necessarily mean you will pay tax on it in Belgium—especially if there is a double taxation treaty with your home country—but the value of that property is used to determine your "global tax rate." Since 2021, the rules have changed, and the Belgian authorities now assign a "Cadastral Income" (Revenu Cadastral) to foreign properties based on their market value.

You will need to provide the address, the type of property, and its estimated value to the tax office. They will then send you a document confirming the Cadastral Income you should use in your Tax-on-web filing. This is a common pain point for British and American expats who own homes back home. Failure to report this can lead to massive back-taxes and penalties later on. It is a nuanced area, so checking the specific codes for foreign property in the Tax-on-web help files is essential.

Maximizing Deductions and Tax Credits

Belgium has some of the highest income taxes in the world, but it also offers a surprising number of ways to lower that bill. Many of these deductions are not automatically filled in, so you must hunt for them. The most common ones include childcare costs, charitable donations, and "service vouchers" (titres-services). If you have a cleaner or a gardener paid via the official voucher system, you get a significant tax credit for every voucher used.

Another huge deduction is the "long-term savings" and "pension savings." If you have a Belgian pension savings plan with your bank, they will send you a certificate (Fiche 281.60). You must manually enter the amount paid into Code 1361 or similar. This can result in a tax reduction of up to 30% of the amount you saved. For a detailed list of what you can claim, refer to our guide on Deducting Professional Expenses: Flat Rate vs Actual Costs.

Childcare and Charity Deductions

If you have children in a crèche, after-school care, or summer camps, these expenses are tax-deductible up to a certain daily limit per child. The organization should provide you with a fiscal certificate. In Tax-on-web, look for the section dedicated to "Dépenses donnant droit à une réduction d’impôt." You enter the total number of days and the amount paid. This is one of the most effective ways to reduce your tax burden if you are a parent. You can read more about the specifics in our article on Tax Reductions for Childcare Expenses (Crèche and Camps).

Charitable donations are also beneficial, but only if the organization is "recognized" by the Belgian government. Most major NGOs like the Red Cross or Médecins Sans Frontières will automatically send your data to the tax office, but smaller local charities might not. Ensure you have a receipt for any donation over 40 euros. These donations can reduce your tax by 45% of the donated amount, which is a fantastic incentive to give back to the local community.

Pension Savings and Service Vouchers

As mentioned, the "titres-services" or "dienstencheques" system is a pillar of Belgian life. Every voucher you buy for 9 or 10 euros actually costs you significantly less after the tax deduction. The company (like Sodexo/Pluxee) will provide an annual statement. Make sure this number is entered correctly in your return. It’s one of those "hidden" benefits that makes the high cost of living in Belgium a bit more manageable.

For those looking at long-term wealth, the pension savings schemes (épargne-pension) are essential. Even if you only contribute a small amount each month, the tax credit is substantial. However, there is a cap on how much you can contribute each year to get the maximum benefit. If you are an employee, your company might also offer a "group insurance" (assurance groupe). This is often taxed differently, but it's worth checking your annual summary to see if there's anything you need to report.

Deduction Type	Max Deduction / Credit (Approx)	Required Document
Pension Savings	30% of contribution	Fiche 281.60
Childcare	€15.70 per day per child	Fiscal Certificate from provider
Service Vouchers	15% to 30% (Region dependent)	Annual Statement from Pluxee/Edenred
Charitable Giving	45% of donation	Receipt from recognized ASBL/VZW
Professional Costs	Flat rate or actual costs	Invoices/Salary Fiche

Final Submission and What Happens Next

Before you hit the final "Submit" button, look for the button that says "Calculer les impôts" or "Belasting berekenen." This is the moment of truth. The system will run a simulation based on your entries and tell you exactly how much you will get back or how much you owe. If the number looks wildly wrong—for example, if it says you owe 10,000 euros—do not submit. Go back and check your entries. A common mistake is entering a comma instead of a period, or putting a number in the wrong box (like accidentally putting your gross salary in the "tax withheld" box).

Once you are satisfied, you sign the return digitally (again, using Itsme). You will receive a confirmation message and a PDF copy of your return. Download this and save it! You will need it if you ever apply for a mortgage or if the tax office asks questions later. The official "Assessment Notice" (Avertissement-Extrait d'Imposition) usually arrives by mail or via your e-Box (the government digital mailbox) between 3 and 12 months later.

Checking the Calculation Tool

The calculation tool is surprisingly accurate, but it only knows what you tell it. If you have a complex situation, such as working part-time in another country or having a "special" status, the tool might struggle to give an exact figure. However, for 95% of expats, that "Simulation" result is what you can expect to see in your bank account a few months later. If you are surprised by a high bill, it might be worth checking if your employer has been withholding enough tax. You can cross-reference this with your monthly payslips as explained in How to Read Your First Belgian Payslip (Fiche de Paie).

If you discover an error after you have submitted, don't panic. You can usually modify your return once through the portal before the deadline passes. If the deadline has already passed, you will have to file an official "protest" or "reclamation" once you receive your final assessment. This is a more formal process, which we detail in How to Contest an Incorrect Tax Assessment Notice (Avertissement-Extrait).

The Assessment Notice (Avertissement-Extrait)

When the final "brown envelope" arrives (or the PDF in your e-Box), it will tell you the final result and the deadline for payment or the date of your refund. If you owe money, you usually have two months to pay. If you are getting a refund, the state typically pays it out at the end of the second month following the month the notice was sent. For example, if you get your notice in October, expect your money at the end of December.

It is important to keep these documents for at least seven years. The Belgian tax authorities have the right to audit your past returns within this timeframe. If you move house, make sure your address is updated at the commune so these documents reach you, or better yet, activate your "e-Box" to receive everything digitally. This ensures you never miss a payment deadline simply because a letter got lost in the mail.

Important Tax Disclaimer

This guide is intended for informational purposes only and is based on the general tax rules in Belgium. Tax laws are subject to frequent changes and can be interpreted differently based on individual circumstances, such as nationality, residency status, and specific employment contracts. We are not certified tax advisors or legal professionals. We strongly recommend consulting with a qualified Belgian tax accountant (comptable/boekhouder) or contacting the SPF Finances directly before submitting your final tax return to ensure compliance with the most current regulations.