Post merger integration checklist for Europe: the HR steps from signing to Day 100

In 2026, a post merger integration checklist for a deal in the Netherlands follows four stages. At signing, decide who employs the buyer’s people and map consultation duties. Before closing, recruit and sponsor the first roles. At closing, keep payroll running and have retention offers ready. After Day 100, consolidate payroll and HR policies.

This guide follows the HR steps from signing to Day 100, with Dutch rules as the worked example.

What does a European deal add to a post merger integration checklist?

A European deal adds legal steps that a standard US M&A integration checklist rarely covers. Employees have strong dismissal protection, and employee bodies have a say. Meanwhile, the buyer often has no local employer yet. Seven risks come up in almost every deal.

No at-will employment

A dismissal needs a valid reason, a set procedure and often a statutory payment. So US-style synergy plans need a longer timeline. Read why there is no at-will employment in Europe.

Works councils and unions

In 2026, the Dutch Works Councils Act (WOR) requires a works council at companies with 50 or more employees. The company must ask that council to advise on an intended transfer of control. It must ask early enough for the advice to shape the decision. If the company then decides against that advice, it must wait one month. In many Dutch deals, the SER Merger Code also requires the parties to inform unions before they reach agreement.

Gun jumping

Until closing, the seller still owns the target. The buyer therefore cannot direct its staff or change their terms. See what HR can do before a deal closes.

No employer for your own people

Integration leads and transferees need a lawful employer in the Netherlands from their first day. The usual routes are a Dutch BV, non-resident employer registration or an employer of record. Compare them in who employs your people between signing and closing.

Payroll registration

A foreign company that employs staff in the Netherlands must register as an employer with the Dutch Tax Administration. Our guide to the loonheffingennummer explains the steps.

Hidden people liabilities

Collective agreements (CAOs), sector pension funds, long-term sick leave and misclassified contractors rarely stand out in a data room. Our HR due diligence checklist lists what to request.

Automatic transfers

In a share deal, the employer stays the same. However, when a business or part of it transfers, EU Directive 2001/23/EC moves its staff to the buyer. They keep their existing terms. Carve-outs often add a transition services agreement for HR.

The post merger integration checklist, stage by stage

The table turns these risks into an acquisition integration checklist for each stage. Use it next to your deal timetable, because consultation and permits often set the pace, not the closing date.

Stage	Main risks	What to have in place
At signing	Late consultation, unknown liabilities, no employer for the buyer’s hires	Due diligence red flags with owners, a consultation map per country and a decision on who employs the buyer’s people
Before closing	Gun jumping, slow permits, key people leaving	First integration hires on a lawful employer, permit applications for non-EU hires and joint staff messages agreed with the seller
At closing (Day 1)	Missed or wrong payroll, unclear reporting lines	A registered and tested payroll, a documented consultation outcome and signed retention offers
After Day 100	Two sets of terms, unlawful data transfers	Staff moved from an employer of record to your own entity, one payroll and one set of HR policies, and HR data moved under a lawful GDPR transfer route

The last stage depends on having your own entity. That is one reason many US buyers set up a European headquarters in the Netherlands.

What is Day 1 readiness for HR in a post merger integration checklist

Day 1 readiness means everything people rely on works on the day the deal closes. For HR, that means a lawful employer, a working payroll and valid permits. It also means a documented consultation outcome and signed retention offers. If one item is missing, staff notice quickly, often in their first paycheck. Before closing, test your Day 1 readiness against this list:

• Employer: every person has a signed contract with an employer that can lawfully employ them.
• Payroll: the payroll is registered, a test run is complete and pay dates stay the same.
• Permits: highly skilled migrants need an employer that is an IND recognised sponsor. As of November 2026, the IND lists a statutory decision period of 90 days for these permits. US nationals who represent a US company in a key position may qualify under the DAFT instead.
• Consultation: the works council’s advice is in, the decision is recorded and any waiting period has passed.
• Retention: key people have signed offers before news of the deal spreads. Our guide to employee retention strategies covers what keeps people after the offer.
• Communication: staff know who their manager is and whom to ask about pay.

What comes after Day 100 on your post merger integration checklist?

After Day 100, the work shifts from keeping things running to building one organization. People employed through an employer of record move to your own entity once it is ready. Payroll and HR policies then come together, and HR data moves to group systems. In Europe, each of these steps has its own legal route.

• Moves from an employer of record: each move needs a new contract that the employee accepts. Because the facts matter, ask counsel how earlier service counts.
• Harmonizing terms: individual contracts generally change only with the employee’s agreement. In addition, where a works council exists, changes to rules on working hours or pensions need its consent.
• Collective agreements: a sector-wide CAO can still set minimum terms that you cannot go below.
• Restructuring: job cuts follow Dutch dismissal rules, and larger rounds add extra steps. Our guide to collective dismissal in the Netherlands explains the route.

Who owns HR integration, and when do you need outside help with a post merger integration checklist

The buyer’s HR lead usually owns HR integration, inside the wider integration team. Deal counsel handles the legal steps. Outside help makes sense when the buyer has no European entity or local HR team. It also helps when the deal involves a works council, permits or several countries at once.

Whoever owns it, someone has to employ people locally, run Dutch payroll and meet the works council. A post acquisition integration often stalls on these local tasks, not on strategy. So give each item on your HR integration checklist a named owner. A typical split looks like this:

• The buyer’s HR lead owns the plan, the budget and any decisions on terms.
• Deal counsel advises on consultation, transfers and dismissals.
• The target’s HR and payroll team handles day-to-day delivery and staff questions.
• A local employer or employer of record employs the buyer’s early hires until its own entity exists.

Get the full briefing behind this post merger integration checklist

Our briefing for US acquirers covers every step from signing to Day 100 in more depth. It is written for deal and HR teams buying in Europe. To receive it, request the full briefing.

For nearly 40 years, Octagon has helped organizations move talent into and across Europe on a compliant footing. We employ your people in the Netherlands until your entity is ready, then transfer them. As an IND recognised sponsor, we also apply for permits for the non-EU staff we employ. Read our guide to an employer of record in the Netherlands, or email sales@octagon.nl.

Frequently asked questions

What happens in the first 100 days after an acquisition?

In the first 100 days, the buyer takes control and steadies the business. For HR, that means paying everyone on time, keeping key people and starting agreed changes. In Europe, new terms or job cuts still need consultation and a valid legal route. Plan them as projects, not quick fixes.

What is Day 1 readiness in M&A?

Day 1 readiness is the set of tasks that must work when a deal closes. Examples include bank access, IT and payroll. For a European target, HR adds several items. Staff need lawful contracts and valid work permits. Consultation must be complete, and key people should have signed retention agreements.

What should HR do before a deal closes?

HR should prepare everything that sits inside the buyer, without running the target. Typical tasks include following up due diligence findings, mapping consultation, hiring integration staff and filing their permits. Retention offers usually go through the seller. Instructions to the target’s employees, however, have to wait until closing.

General information as at November 2, 2026, not legal or tax advice.