A fixed interest rate can turn a friendly loan into annual tax evidence.
Picture a small retailer in Haarlem with rent due, staff to pay, and invoices on the desk. After a few good years, he has kept money outside the company and lends €300,000 to a relative for a second home. The deal is neat: twenty years, interest only, 4.5 percent fixed, no penalty-free early repayment. No bank desk, no trading screen, no daily price. Just a private loan between people who know each other. That makes Dutch Box 3 control a records problem, not only a private tax calculation.
Private wealth now needs a record
Then comes the Belastingdienst Kennisgroepen position published on 22 May 2026. It deals with a technical Box 3 question. In business terms, it says something simple: a private fixed-rate loan is not just a number copied into the tax return. It is a valuation story that must stay consistent from one year to the next.
The loan has two values
The starting point is Article 5.19 of the Dutch Income Tax Act 2001. Box 3 assets and debts are taken at fair market value. For cash, that is straightforward. For a fixed-rate private loan, the value moves when market rates move.
If comparable market rates fall below the fixed 4.5 percent, the lender holds a claim that pays more than a new comparable loan. That claim is worth more than the nominal €300,000. The debtor’s debt also has a higher fair market value. If comparable market rates rise above the fixed rate, the value moves the other way.
Timing is part of the tax story
In the official example, the €300,000 claim is valued at €319,701 at the beginning of year two. The comparable market rate is 4.0 percent, and nineteen years remain. The point is not family feeling or a tidy contract. The point is the present value of the cash flows.
That value is built by discounting future interest and principal payments. The rate has to fit comparable terms: maturity, collateral, debtor risk, repayment schedule and similar conditions. Non-tradability does not in principle change fair market value. Collection risk can lower the claim. For the debt, the relevant question is whether the creditor may forgive it.
The shortcut is not casual
Belastingdienst also recognises the administrative burden. For practical reasons, a taxpayer may use nominal value for a monetary claim or debt, other than a security, if the choice is consistent and not made merely for tax advantage. That sounds generous. It only works if the file stays disciplined.
The same nominal-value method has to run through both the forfaitary calculation and the actual-return counter-evidence route. It has to cover opening and closing values, plus deposits or withdrawals linked to acquisition or disposal. That matters because actual return in Box 3 includes income and value changes. It also matters because taxpayers gather their own data for the Opgaaf werkelijk rendement. The form is not the whole file. The papers around it matter.
For 2026 provisional assessments, Belastingdienst still uses the bridging rules, not the actual-return system that is only known after year-end. The published percentages are 6.00 percent for investments and other assets, 2.70 percent for debts, and 1.28 percent for bank balances. Those rates do not erase the valuation question. They sit beside it.
A market rate is not wallpaper
For many small entrepreneurs, the hard part is the comparable market rate. There is no single official rate to paste onto every private loan. DNB publishes useful bank mortgage-rate data. It also says mortgage rates depend on risk class and fixed-interest period, and that published averages can differ from current advertised rates because of timing, loan-to-value differences and aggregation.
What founders should separate
That makes the loan file important. I would not trust a folder that stops at the signed agreement. The useful papers are the agreement, the fixed-rate period, collateral, remaining maturity, repayment limits, debtor quality and payment history. Also keep the reason a chosen market comparison was reasonable on the valuation date. This is ordinary administration. It is done before memory starts editing the facts.
2028 does not remove 2026
The planned Wet werkelijk rendement box 3 gives the subject a wider frame. The government wants a new Box 3 system from 1 January 2028 based on actual return. The Tweede Kamer has adopted the bill, and the Eerste Kamer still has to consider it. The government has also said it is considering changes, especially around the effects of the wealth-accretion approach from 2028.
For private loans between natural persons, the explanatory memorandum points toward a nominal valuation rule to limit the burden on taxpayers. That explains the policy direction behind the practical approach. It does not make 2026 disappear. Until the new system is in force, the present question remains simple enough to ask and hard enough to answer: is the taxpayer using fair market value, or nominal value, and can the choice be explained without looking opportunistic?
Back to the retailer in Haarlem. The family loan may still be normal, commercial and well intended. The borrower still plans to pay €300,000 back. The lender still receives the agreed interest. Nothing in daily life feels altered. Yet for Box 3, the tax value may move when the market rate moves, unless the taxpayer uses the practical nominal route consistently.
That is the real lesson. A private loan can look still on paper while moving for tax purposes. The safer mindset is not fear of a formula. It is respect for continuity. Choose a valuation story that fits the facts. Keep the papers that support it. Do not let a convenient year-end number become the weakest part of an otherwise honest arrangement.
Sources
- Belastingdienst Kennisgroepen
- Wettenbank
- Belastingdienst
- Belastingdienst
- Belastingdienst
- Rijksoverheid
- Rijksoverheid
- Rijksoverheid
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