Complete your tax return

Complete your tax return

It's time to fill in your tax return again. And, yet again, the search is on for all the documents you need in order to complete the form. Here, we tell you a few things that you certainly must keep in mind when completing your tax return.

Due date for submitting your return

Online submission

If you use Tax-on-web to do your tax return, you have until 15 July 2024


Don't leave it till the eleventh hour to fill your tax return in, and so avoid any nasty surprises.

Submitting your tax return: on paper or online?

Filling your tax return in online using Tax-on-web is by far the preferred method, since it offers a number of advantages.

  • You get more time to fill the return in.
  • A number of figures that the tax office receives electronically are filled in from the outset: property tax, salary and wages, pensions, replacement income, service voucher outlays, gifts, pensions savings and certain standing details concerning your credit. However, we still advise checking the captions for which figures come filled in, especially gifts and property tax.
  • Sending it electronically is simpler. You don't have to enter any codes, thus reducing the risk of error. The online help function and handy wizards help you fill in your return and calculate your tax liability.
  • If you enter certain details incorrectly or omit them, you'll get an error message on the screen straight away.
  • You immediately get an estimate of how much your tax rebate or supplement will be.
  • You can continue to refer to the return after it's been sent. Even if you've already sent it in, you can correct any errors or omissions yourself up till 15 July 2021 (once only).
  • The tax office will process your return quicker, so you'll also get your final assessment sooner.
  • In order to login to, you need your electronic identity card, or a security code from a mobile app or token or from itsme.

Needed in order to complete your tax return

We advise you to first gather this information together before you start with filling in the tax return.

  • The number of the bank account for any tax refund that may be due to you.
  • Full details of your income: salary slips, rental income, maintenance, pensions, etc.
  • Details of your occupational expenses (if you are not claiming the lump-sum figure).
  • Tax certificates for your mortgage loan payments and mortgage protection insurance (if it qualifies for tax deduction).
  • Tax certificates for 'green' loans taken out to finance energy-saving investments (from 1 January 2009 to 31 December 2011) such as for solar panels, a central heating boiler, floor, wall or roof insulation, or double glazing.
  • Documents vouching payments into pension schemes.
  • Documents vouching payments into long-term savings schemes.
  • Documents vouching child-minding costs (for children under 14 - 21 if they're seriously disabled).
  • Details of payments made to local employment agencies (PWA vouchers).
  • Details of payments made by your for services paid for using service vouchers.
  • Other items for which tax relief can be claimed, such as certificates of donations, roof insulation bills, expenses to protect your home against fire and break-in (only in Brussels) and profit-sharing certificates in recognised development funds.
  • Details of any prepayments made for assessment year 2024.
  • Details of maintenance payments you've paid.


You should keep all documents you use for filling in your tax return for a period of seven years.

Don't just copy the figures from last year's return!

It'll do no harm to use your previous return as a reference. You'll see what information you provided then and should not be forgetting this year. But do be careful: amounts can vary from year to year, and codes change as well.

Where to claim your tax reliefs

Mortgage loan (home loan) – section IX

The tax benefit with such expenditure on an owner-occupied home depends on the region in which the taxpayer is resident for tax purposes on 1 January of the assessment year.

Long-term saving for individual life insurance policies – section IX

In income year 2023 (assessment year 2024), payments eligible for federal long-term saving schemes are tax-deductible up to 2,350 euros. Long-term savings qualify for tax relief of 30% of the actual deposits or 705 euros for each person claiming the maximum. Enter your payments into the scheme in code 1353 (for men) or 2353 (for women) in the return.

Find out more about long-term saving.

Pension saving – section X

Last year, you've been able to set your maximum limit at one of two figures.

Option 1:
You saved up to 990 euros in 2023 and benefit from tax relief amounting to 30% of the sum you save.

Option 2:
You saved up to 1,270 euros in 2023. You qualify for a tax benefit of 25% on the sum you save if it exceeds 1,188 euros.

You cannot claim tax relief on pension savings on top of the allowance for acquiring employer shares.

Pension savings at KBC

Further help

Information booklets are enclosed with returns in paper form. Guidance is also available on the tax office website.