What the 31 December date changes
A deduction belongs to the year the money was paid, not to the year of the return. A payment made on 30 December counts for the year that is ending, the same payment on 2 January counts for the next one. That is the only thing the date changes, and it is what gives this tool its name.
The model carries no room from one year to the next. Room left under a plafond on 31 December drops out of the following year's calculation, which starts again from the full plafond. A €3,200 plafond filled to €1,200 therefore leaves €2,000 that will not come back.
Three lines are followed here: private pension savings, capped at €3,200 a year, home savings at €672 and insurance premiums at €672. Together they make €4,544 of annual plafond.
What the room left is worth
The room is the difference between the plafond and what has already been paid. On the starting values, €1,200 of private pension savings leaves €2,000, and the two empty lines leave €672 each. The total is €3,344.
What that room represents depends on the marginal rate, which the income and the tax class decide. On €60,000 it is 39% in classes 1 and 1a and 18% in class 2. The same room therefore does not carry the same weight from one situation to the next: a little over two to one between class 1 and class 2.
Income counts as much as the class. In class 1 the marginal rate is 18% at €30,000 and 32% at €45,000, then reaches 39% at €54,090 and stays there to €117,450. Above the taxable threshold, a euro of room filled is therefore worth between 8 and 42 cents of tax.
How to use the optimizer
Three amounts to enter: what has already been paid this year into private pension savings, home savings and insurance premiums. The income and the tax class set the marginal rate, which is what a deducted euro is worth.
The big number is the room left across all three lines. The tax it represents is reserved for the Pro plan. The room itself, the countdown, the marginal rate and the chart stay readable without an account.
All five settings fit in the page address. The Copy link button returns a URL that reopens the same amounts.
- Annual income and tax class: they set the marginal rate.
- Amounts already paid: the year's running total on each of the three lines.
- Room left: the sum of the gaps between each plafond and its amount.
Reading the result
The two swatches above the chart separate what has already been paid from what is left under the plafonds. The chart makes the same split line by line, which shows where the room comes from.
A full bar marks a plafond already reached: a further payment on that line no longer enters the calculation. A short bar marks the opposite, a line where a payment still counts in full.
The countdown starts from today's date and stops on 31 December. It changes no amount on screen: it only says how many days separate the simulation from the end of the tax year.
Frequently asked questions
Which payments count for the current year?
Those made before 31 December. A deduction belongs to the year of the payment, not to the year of the return. The three lines followed here are private pension savings, home savings and insurance premiums, capped at €3,200, €672 and €672 a year.
Which ceilings apply before the end of the year?
€3,200 a year for private pension savings, €672 for home savings and €672 for insurance premiums, so €4,544 for the three lines in this tool. These amounts are approximate and do not vary here with the tax class, age or the number of children.
How do private pension savings work?
They are retirement savings whose payments during the year are deductible up to €3,200 in this model. That is the highest plafond of the three lines followed here, so it carries most of the room: on the starting values, €2,000 of the €3,344 of room comes from it.
When does a year-end payment change nothing?
In three cases. The line's plafond is already reached, so the room is zero. The income stays under the taxable threshold, €13,230 in class 1, so the marginal rate is zero and the deduction represents nothing. Or the payment lands after 31 December, and belongs to the following year.
How much is a year-end payment worth?
The amount paid multiplied by the marginal rate, which the income and the tax class decide. On €60,000 that rate is 39% in classes 1 and 1a and 18% in class 2, so the same payment does not represent the same thing from one situation to the next. The figure itself appears in the Estimated tax saved box, which is reserved for the Pro plan.
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