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Invoices and professionals · Everyday tools

Accountant’s toolbox: seven everyday calculations

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Seven free tools for everyday checks: calculate VAT and late payment interest, create a structured payment reference, check an IBAN or an enterprise number, count working days and draw up a depreciation schedule. For example, €1,000 excluding VAT at 21% comes to €1,210.00; an invoice of €1,000 paid 60 days late by a business entitles you to €17.26 in interest and €40 in compensation.

Each tool cites its source and calculates in your browser: no number or amount is sent. The results are indicative and do not replace an accountant’s advice.

The seven tools

  • Calculate VATFrom excluding VAT to including VAT and back, at 21, 12, 6 or 0%, over several lines. Example: €1,000 excluding VAT at 21% = €1,210.00 including VAT.
  • Late payment interestWhat you can claim on an unpaid invoice, between businesses or from a consumer. Example: €1,000 paid 60 days late by a business: €17.26 in interest and €40 in compensation.
  • Structured payment referenceCreate or check a structured payment reference +++123/4567/89012+++. Example: invoice 2026001234 gives +++202/6001/23464+++.
  • Check an IBANCountry, length and check digits of any IBAN in the SEPA area. Example: BE68 5390 0754 7034: valid Belgian IBAN (16 characters).
  • Check an enterprise numberBelgian CBE (Crossroads Bank for Enterprises) or VAT number: format and check digits, with a link to the CBE. Example: 0878.065.378 is valid; VAT number: BE0878065378.
  • Working days and deadlinesA due date in calendar, working or banking days, with Belgian public holidays. Example: 10 working days after 1 May 2026: 18 May 2026.
  • Depreciation scheduleStraight-line or declining-balance, under Belgian tax rules, with the pro rata rule for companies. Example: €10,000 over 5 years: €2,000 a year straight-line; €4,000, then €2,400 declining-balance.

Due dates and invoices

  • Tax and social calendarVAT, advance tax payments, withholding tax (bedrijfsvoorheffing / précompte professionnel), DmfA (quarterly social security declaration), social security contributions, corporate income tax: all 2026-2027 due dates, filtered by profile and exportable as .ics.
  • Read and check an invoiceA Peppol or PDF invoice: details, calculations, VAT rates, IBAN and payment reference.
  • Prepare my VAT returnThe boxes for the period, from your invoices.
  • Rent indexationThe new rent based on the health index and your Region’s rules.
  • Pay for the director of an SRLRemuneration, dividends and liquidation reserve: the director’s net income.

Why these checks matter

A wrong structured payment reference or IBAN delays a payment; a miscounted deadline loses you a right; a wrong VAT rate costs you at an audit. Check digits (modulo 97) catch most typing errors, but they do not prove that the number belongs to the right person: a supplier IBAN that changes should always be checked by phone.

Frequently asked questions

Are these tools free?

Yes, with no limit, no sign-up and no cookies. The calculations run in your browser: nothing is sent to Indexo.

Are the results as good as an accountant’s advice?

No. They apply the published rules, cited on each page, but they do not know your file. For a decision, ask your accountant or the competent authority.

How can you check several invoices or numbers at once?

Each tool handles one case at a time. Batch processing for accounting firms will be part of Indexo Pro, which is not yet available.

What next?

Sources

Parameters in force on 1 October 2026. Each parameter links to its source, the official one where it exists; a secondary source is flagged as such.