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Construction subcontracting in Belgium: 30bis withholding

A check before every payment, social and tax withholding, works notification and an on-site attendance register.
October 2, 2026 by
Construction subcontracting in Belgium: 30bis withholding

You check the official database when the contract is signed, print the result, and keep paying for months without going back to it. In Belgium, the regime known as "30bis" requires a check before every payment, not just the one at signature: a check only covers the payment it is tied to.

Who the application is for

For construction firms that use subcontractors in Belgium and need to check their standing before every payment, notify certain sites and keep an attendance register. It installs on top of a shared subcontracting foundation, from which it takes its sites, contracts and payments.

What the application does

  • Adds a Belgium-specific compliance check source, with a detailed result that tells a social debt apart from a tax debt.
  • Works out the withholding according to the debts found, and applies the company's maximum setting when no valid check covers the payment.
  • Carries the subcontractor's business registration number, the key to the official check.
  • Keeps the site's works notification, with its applicable threshold set by the number of subcontractors on site, and blocks payment until it has been filed.
  • Keeps the on-site attendance register, with the person, their employer and their arrival and departure times.
  • Refuses a check with no end date: under this regime, a check is valid for one payment only, never for a fixed period.

Day to day

  1. Set, on your company, the withholding rates and the notification thresholds: these are settings to confirm with your payroll body, not fixed values.
  2. Enter the business registration number of each subcontractor.
  3. Before every payment, check the official Belgian database and record the result: compliant, or non-compliant with the debt or debts found.
  4. If the site has one or more subcontractors beyond the applicable threshold, file the works notification before any payment linked to that site.
  5. Keep the attendance register day by day: person, employer, arrival and departure times.

What the application does not do

  • It does not connect to any official portal: checks and notifications are done on the portals themselves, and their result is recorded here with its reference.
  • It does not pay anything over to an authority: the withholding is calculated and recorded, but paying it over is a matter for your accounts.
  • It does not offer any validity period for a check: under this regime none exists, the rule being to check before every payment.
  • It does not decide whether an extra document you add should block payment: that setting remains yours to make.
  • This application is designed for subcontracting in Belgium; the 30bis regime changes over time, and it does not replace the advice of a professional or the relevant authority.

Getting started

Have your payroll body confirm the withholding rates and notification thresholds before setting them on your company: the values supplied are usual starting points, not regulatory citations. Then enter the business registration number of each subcontractor, and decide whether your own contractual documents should block payment.

Going further

To find out whether this application suits your business and how to activate it, compare the plans or write to us.

Compare the plans

Write to us

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