The Belgian capital gains tax is no longer theoretical. It applies to realised gains on financial assets from 1 January 2026, with the value on 31 December 2025 acting as the starting point for assets already held before 2026. The practical consequence for entrepreneurs: when shares are later sold, transferred or reorganised, you need to explain where the starting value came from.
That is why we built the Belgian capital gains tax hub: one landing page for the new rules, plus deeper pages on the reference value, substantial shareholdings, formula-based valuation and the role of the accountant or statutory auditor.
1. The date that moves the taxable base
For shares acquired before 1 January 2026, the tax calculation looks at the snapshot moment: the value on 31 December 2025. The later gain is generally measured from that value, not from the historic acquisition price, except where transitional rules or an evidenced higher acquisition value change the outcome.
A low or weakly documented starting value flows through every later calculation. A higher, defensible 31 December 2025 reference value does not automatically reduce tax, but it gives you a coherent position when a sale happens.
2. When 20% becomes a different regime
Not every shareholder falls into the same regime. For substantial shareholdings, generally from at least 20% of the rights in the company at the moment of disposal, a special regime applies: an exemption up to EUR 1 million over five years and a progressive scale above it. Transfers outside the EEA and internal sale structures can again be treated differently.
That makes the reference value more important, not less. The question is not only what the shares are worth later, but which shareholder position, transfer form and exemption band applies. We unpack that logic on substantial shareholdings and rates.
3. Formula-based is not a strategy
For unlisted shares, a formula or safe-harbour style valuation can look attractive, especially when time is short. But a formula such as equity plus a fixed EBITDA factor rarely captures the true economic value of a company: growth, margin quality, customer concentration, owner dependency, normalisations and transferability all collapse into one rough proxy.
That is why the choice between formula-based and professional valuation is not a technical footnote. A professional valuation records methods, normalisations and assumptions. The fiscal reference value method shows how that file differs from a formula fallback.
4. The accountant makes the file defensible
A valuation report is only useful when it connects to the accountant’s file: annual accounts, ledger data, normalisations, shareholder structure and supporting evidence. The accountant or statutory auditor should not have to trust every valuation engine blindly; they should be able to see which sources were used, which corrections were applied and why each method carries weight.
That is why Upswitch is not positioned as a tax shortcut, but as a file engine. The workflow builds a valuation with an audit trail, after which your accountant reviews how it applies to your situation. More on that role sits at accountant and statutory auditor review.
5. What to do this week
- List which shares were held before 2026 and who holds the rights at the moment of transfer.
- Collect the latest approved annual accounts, ledger detail, shareholder register and relevant 2025 transactions or capital increases.
- Calculate a first reference value with a professional method mix instead of relying only on a formula.
- Ask your accountant or tax adviser to review normalisations and shareholder position.
- Store the report, data sources and review notes together, so the file remains reproducible later.
Waiting does not necessarily remove rights by itself, but it often removes context: details about exceptional costs, management fees, intercompany agreements and 2025 transactions get scattered. The page on the 31 December 2027 deadline explains why organising documentation on time is the rational move.
Frequently asked questions
Does every entrepreneur need a reference value now?
Not every situation requires the same depth. But entrepreneurs with unlisted shares held before 2026, a possible sale, gift, transfer or reorganisation benefit from a reproducible value and a file that preserves the data used.
Is the 31 December 2025 value always required?
For assets acquired before 2026, the 31 December 2025 value is the central snapshot moment in the new rules. Transitional nuances exist, such as an evidenced higher historical acquisition value in certain cases. Confirm the concrete application with your adviser.
Why is a formula valuation risky?
A formula is fast, but often misses company-specific value drivers such as growth, normalisations, customer risk, market position and transferability. That can make the starting value lower than a professional valuation supported by multiple methods.
Can Upswitch calculate my exact capital gains tax?
Upswitch builds the valuation basis and report. The effective tax depends on shareholding, sale form, exemptions, exceptions and your tax return position. Always validate that conclusion with your accountant or tax adviser.
Upswitch is the M&A infrastructure layer for the European SME economy. Defensible valuations and structured transaction matching for the lower mid-market.