Voorlopige aanslag (provisional tax) — what does this mean?
Why you get one, whether it's too high/low, how to adjust it, when you really must top up, consequences of ignoring it.
Project your provisional tax assessment
Combines Box 1 income + already-withheld payroll tax + mortgage interest deduction + Box 3 wealth tax. Positive = you owe; negative = you get back.
Pay / receive€0estimated for 2026
Per quarter (4× spread)€0
Box 1 tax (after credits)€0
Box 3 tax€0
Total tax owed vs already paid
€0How we got there
- Box 1 raw tax€0
- − Mortgage interest deduction (36.97%)− €0
- − Tax credits (AHK + AK)− €0
- Box 1 net€0
- + Box 3 wealth tax+ €0
- Total tax owed€0
- − Already withheld− €0
- = Pay / receive€0
Indicative 2026 model. Excludes Box 2 income, partner-specific allocations, multi-year carry-forwards, and uncommon deductions. For exact aangifte: Mijn Belastingdienst.
In short
A provisional assessment (voorlopige aanslag) is an estimate of the income tax you'll pay or receive back for the current or upcoming year. Belastingdienst sends it based on prior year or your own request. Two flavors: (1) To pay: monthly top-up installment, usually for ZZP'ers, people with multiple income sources, or owned-home owners with high deduction the employer doesn't apply. (2) To receive: monthly payout of credit, e.g., mortgage interest deduction over-withheld. 11 installments: January to November, final assessment follows May next year. Important: provisional assessment is not a payment obligation — you can adjust or cancel via Mijn Belastingdienst if your situation changes. But: if you underpay on provisional + final turns out much higher, then tax interest 8% per year on underpayment (2026). Tip ZZP'ers: request provisional assessment the moment you generate serious revenue — prevents May shock + spreads cashflow. Tip owned-home owner: provisional refund for mortgage interest means monthly inflow instead of one big refund in May.
You enter
- Amount on current assessment — The monthly installment Belastingdienst currently collects or pays. On the letter.
- Expected collective income 2026 — What you'll earn this year (wage + profit + dividend + other). Realistic, not conservative.
- Employment income + employer withholdings — What employer already withholds for wage tax. Reduces needed provisional.
- Expected ZZP profit — Estimated annual profit after business costs. No employer withholding = full IB+ZVW you pay yourself.
- Owned-home mortgage interest — For provisional REFUND: annual mortgage interest amount with deduction. Max at 36.97% bracket since 2024.
- Other deductions — Lijfrente, alimony paid, specific medical costs, charitable gifts. Lowers taxable income.
You get back
- Is the assessment correct? — Too high: adjusting prevents cashflow problem. Too low: adjusting prevents May shock + tax interest.
- Recommended installment amount — What the monthly installment should be based on your actual situation.
- Expected final balance May next year — Estimate of what final assessment shows: top-up or refund.
- Tax interest risk — On significant underestimation: how much interest you risk (8% per year on underpayment).
- How to adjust + timing — Direct link to Mijn Belastingdienst + reasoning + timeline for effect.
The math behind it
Provisional assessment = expected IB + premiums − employer withholding − tax credits
Components:
• Expected IB = taxable income × Box 1 brackets (36.97% / 49.5%)
• Employer withholding = what employment employer already pays monthly (wage tax on salary)
• Tax credits = general + employment credit (auto applied by employer, but on ZZP/multiple jobs often partial)
• Box 3 wealth tax = flat-rate or actual return (choice since 2026)
Distribution: amount split into 11 monthly installments (January to November). No installment in December (year-end). Final assessment follows May next year — recalculates with definitive figures.
Tax interest 2026: 8% per year on underpayment, from 1 May next year until payment date. But: no interest on overpayment until 1 May next year.
Components:
• Expected IB = taxable income × Box 1 brackets (36.97% / 49.5%)
• Employer withholding = what employment employer already pays monthly (wage tax on salary)
• Tax credits = general + employment credit (auto applied by employer, but on ZZP/multiple jobs often partial)
• Box 3 wealth tax = flat-rate or actual return (choice since 2026)
Distribution: amount split into 11 monthly installments (January to November). No installment in December (year-end). Final assessment follows May next year — recalculates with definitive figures.
Tax interest 2026: 8% per year on underpayment, from 1 May next year until payment date. But: no interest on overpayment until 1 May next year.
Worked example
Tom — combo employment + ZZP:
• Employment: €40,000/yr (wage tax €13,000 already withheld)
• ZZP profit: €25,000/yr (no withholding)
• Collective income: €65,000
• No owned home, no deductions
Step 1 — Total IB on €65,000: 36.97% (only bracket 1, €65k < €75,518) = €24,030.
Step 2 — Tax credits: general ~€1,300 + employment ~€3,800 = €5,100 back.
Step 3 — Net IB: €24,030 − €5,100 = €18,930.
Step 4 — ZVW: 5.32% × €25,000 (ZZP profit) = €1,330.
Step 5 — Employer already withheld: €13,000.
Step 6 — Top-up: €18,930 + €1,330 − €13,000 = €7,260.
Step 7 — Monthly installment: €7,260 / 11 = ~€660/mo Jan-Nov.
Without provisional assessment you get a bill of €7,260 all at once in May + 8% interest = €581 extra. With provisional: cashflow spread + no interest.
Sarah — provisional REFUND on owned home:
€200,000 mortgage × 4% rate = €8,000 deduction/yr. At 36.97% rate: ~€2,960 tax refund/yr. Provisional refund: €269/mo Jan-Nov on account — instead of €2,960 all at once in May.
• Employment: €40,000/yr (wage tax €13,000 already withheld)
• ZZP profit: €25,000/yr (no withholding)
• Collective income: €65,000
• No owned home, no deductions
Step 1 — Total IB on €65,000: 36.97% (only bracket 1, €65k < €75,518) = €24,030.
Step 2 — Tax credits: general ~€1,300 + employment ~€3,800 = €5,100 back.
Step 3 — Net IB: €24,030 − €5,100 = €18,930.
Step 4 — ZVW: 5.32% × €25,000 (ZZP profit) = €1,330.
Step 5 — Employer already withheld: €13,000.
Step 6 — Top-up: €18,930 + €1,330 − €13,000 = €7,260.
Step 7 — Monthly installment: €7,260 / 11 = ~€660/mo Jan-Nov.
Without provisional assessment you get a bill of €7,260 all at once in May + 8% interest = €581 extra. With provisional: cashflow spread + no interest.
Sarah — provisional REFUND on owned home:
€200,000 mortgage × 4% rate = €8,000 deduction/yr. At 36.97% rate: ~€2,960 tax refund/yr. Provisional refund: €269/mo Jan-Nov on account — instead of €2,960 all at once in May.
How to read the result
- Top-up vs refund — difference mattersTop-up = you pay extra (usually ZZP, multiple incomes, no provisional set up). Refund = Belastingdienst pays you extra (usually owned home, high deductions). Optimal: provisional matches actual situation so May assessment = €0.
- Timely adjustment prevents tax interest8% interest per year on underpayment from 1 May next year. On €5,000 under-payment 12 months later: €400 interest. Adjusting via Mijn Belastingdienst takes 5 minutes — saves hundreds of euros.
- Mid-year adjustment — effect visible quicklyChange via Mijn Belastingdienst: effect next month (~3-5 working days processing). Adjustment in July applies to Aug-Nov installments. Earlier months not adjustable, but difference is settled in May assessment.
- Ignoring = auto debit or warrantBelastingdienst collects via auto debit (your choice) or warrant. No debit + not paying: warrant within 6 weeks = +6% costs + bailiff. Better: adjust to your situation than ignore.
- ZZP'ers: always request provisionalUnless expecting a loss year: provisional spreads cashflow + prevents interest + prevents May shock. On strong growth raise mid-year; on declining profit lower. Freely adjustable monthly via Mijn Belastingdienst.
Key terms
- Provisional assessment
- Estimate of income tax for current year, split into 11 monthly installments. Adjustable via Mijn Belastingdienst.
- Final assessment
- Final reconciliation after fiscal year, usually in May. Compares actual figures with provisional, results in top-up or refund.
- Tax interest
- 8% per year in 2026 (was 6% in 2024). Calculated on underpayment from 1 May next year. No interest on overpayment until 1 May.
- Mijn Belastingdienst
- Portal for returns + adjusting provisional + status check. Login DigiD (NL citizen) or eIDAS (EU citizen).
- Tax credits
- Tax-reducing credits (general + employment). Employer applies automatically; ZZP'ers receive via return / provisional assessment.
- Installment
- One of the 11 monthly payments (Jan to Nov). December: no installment, prep for final assessment.
Frequently asked
Do I have to pay my provisional assessment?
Yes, but you can adjust. Belastingdienst collects via auto debit (if enabled) or sends payment slip. Not paying + no adjustment = warrant within 6 weeks + 6% extra costs. Better: adjust to your actual situation via Mijn Belastingdienst (free, 5 minutes).
How do I adjust my provisional assessment?
Login Mijn Belastingdienst → "Aangiften en aanslagen" → "Voorlopige aanslag aanpassen". Enter new income estimate + deductions. Effect after ~3-5 working days on next installment. Not retroactive — earlier months stay at old amount, difference settled in May.
What if I'm ZZP and have no provisional?
Request one via Mijn Belastingdienst as soon as you have serious revenue. Prevents May shock + spreads cashflow + prevents 8% tax interest. Especially relevant for ZZP >€30,000 profit/yr. With ZZP + employment combo: provisional covers the ZZP portion where employer withholds nothing.
Overpaid on provisional — do I get interest?
No interest on overpayment by Belastingdienst until 1 May next year. After: 8% per year on credit. Practically: final assessment arrives in May so interest barely runs. However: overpayment is opportunity cost lost (money that could have earned interest on savings).
Owned home — do I automatically get a provisional refund?
No, not automatic. Belastingdienst doesn't always know you bought a home or got a new mortgage. Request via Mijn Belastingdienst: mortgage interest + imputed value → calculates monthly refund. Forgetting costs €200-400/mo cashflow + big May refund instead of spread.
What does Belastingdienst do if I underestimate?
Provisional compared annually with final in May. Underpayment = top-up + 8% tax interest on underpaid (from 1 May). No penalty on honest underestimation; penalty on deliberate low-balling (Belastingdienst calls that "incorrect return"). Tip: estimate realistically + adjust mid-year as situation changes.
Complex situations
Edge cases that typical net-pay tools skip but actually matter for a real Dutch tax situation. Each one assumes the basic case above and tells you what changes.
Employment + ZZP — provisional covers ZZP part
Employer withholds wage tax on employment salary — as if that's your only income. ZZP profit stacks on top in Box 1, but employer doesn't know. Effect: big top-up in May. Solution: request provisional based on TOTAL collective income. Belastingdienst deducts employer withholding + calculates monthly installment for ZZP part. Example: employment €40k + ZZP €25k = total IB €19k. Employer already withholds €13k. Provisional calculates on remainder: €6k / 11 = ~€545/mo top-up. No May shock + 8% interest avoided.
Owned home — request provisional refund
Mortgage interest deduction not applied by employer (they don't know). Example: €200k mortgage × 4% rate = €8,000/yr deduction. At 36.97% rate: €2,960 tax refund/yr. Without provisional: get €2,960 all at once in May next year. With provisional refund: €269/mo on account Jan-Nov. Cashflow spread. Apply: Mijn Belastingdienst → voorlopige aanslag → enter mortgage interest + imputed value. Effect: from next month. On rate or home change: adjust.
Volatile ZZP profit — adjust mid-year
ZZP'ers with unpredictable revenue: provisional set end of prior year on prior year, can deviate from reality. Strategy: at quarterly bookkeeper visit or yourself in Mijn Belastingdienst — adjust provisional to actual YTD figures. Example: provisional €800/mo based on prior-year profit €60k. Actual YTD July: trending €90k. Adjust to €1,200/mo for remaining months → year-end fits total. Prevents big May shock + interest.
Multiple income sources — employers withhold too little
Two part-time jobs or employment + side work: each employer withholds wage tax as if his salary is your only income. Both apply tax credits → double credit application → too little total withholding. Effect: top-up in May. Solution: provisional contains all incomes + corrects double credits. Tip: with large second income source, ask one employer NOT to apply tax credits (wage tax statement). Reduces double application directly.
Lijfrente deposit — provisional refund
ZZP'ers and employees who use their annual lijfrente room get Box 1 deduction. Example: €5,000 deposit at 36.97% = €1,850 tax benefit/yr. Get it back via: final May next year and via provisional refund if you request one. Deposit before 31 December so deduction counts this year; provisional refund can start mid-year if you know you'll deposit.
Allowance affair context — Social Safety Net
Old provisional assessment that was wrong due to Belastingdienst error (allowance affair 2018-2021): call Social Safety Net Team 0800-2358-358 free. They can suspend old assessment, arrange recovery decision, custom payment plan. Don't try to solve alone — specialists there have authority to fix things that otherwise can't be fixed.
What this tool doesn't do
This tool tests provisional assessment based on Belastingdienst 2026 formulas. Many complex situations are worked out above. Out of scope: corporate provisional assessment (BV), inheritance tax advance, international tax-spread (cross-border workers). For your actual: Mijn Belastingdienst + accountant on doubt.