On the first day after a merger, employees of the two companies compare pay slips, and every difference that used to be confidential becomes corridor conversation. Buyers usually want a single pay system for the combined organisation, but Vietnamese labour law does not allow agreed contract terms to be cut unilaterally, so pay harmonisation is a legal and psychological exercise at once, never a simple administrative decision.
The legal limits on changing a pay system
Pay is a mandatory term of the employment contract, and changing the salary level or structure of a serving employee requires agreement, recorded in a contract appendix or a new contract. The Labour Code 45/2019/QH14 sets equal pay principles for work of equal value and requires employers to build wage scales, pay tables and labour norms as the basis for recruitment and payment. A merged pay table for the combined organisation must therefore be rebuilt as one formal system, not assembled by mechanically stapling two old tables together.
Where a merger brings restructuring, technology change or economic reasons that make some roles redundant, the employer must follow the separate route of a labour utilisation plan and dialogue with the employee representative organisation, instead of using a pay redesign to push unwanted staff out. Confusing these two routes is the most common source of disputes, and wage violations are now penalised under Decree 283/2026/ND-CP, which replaced Decree 12/2022/ND-CP from 10 September 2026.
Three harmonisation strategies and their real cost
The first strategy is levelling up: every role moves to the higher of the two pay levels for the same job. It is the smoothest for people and the most expensive, and the extra cost is permanent because it enters the fixed payroll. The second strategy is freezing the higher level: staff already paid above the new band keep their pay, while the lower group catches up along a published roadmap. It controls cost but leaves two tiers doing the same work for a long period.
The third strategy is a full redesign: build a new scale based on job value, convert differences into allowances or conditional bonuses, and apply it immediately to new hires while serving staff keep their nominal income protected. In practice most deals combine the second and third routes: protect existing employees’ income as a matter of the buyer’s honour, while closing the old system so that all future growth runs through the new scale.
Managing reactions and internal communication
Employees react most strongly not to absolute numbers but to a sense of unfairness next to the colleague at the adjacent desk. The harmonisation roadmap should therefore be communicated in sequence: publish the job evaluation criteria first, the new pay scale second, and discuss individual amounts only once income protection is settled for affected staff. Workplace dialogue under the Labour Code is the formal channel for hearing and recording concerns before the new system is issued.
On timing, restructuring the pay architecture usually takes two to four pay cycles to negotiate and document through contract appendices, while fully harmonising the payroll can take twelve to twenty-four months depending on the starting gap. Buyers should load the whole transition cost into the deal model at due diligence stage rather than treating it as an HR expense discovered after purchase.
Frequently Asked Questions
How are pay gaps handled?
Gaps must be handled by job value rather than by legacy company: first map equivalent roles across the two systems, identify the group paid less for the same work, then lift that group along a pre-announced roadmap. For staff paid above the new band, the safe practice is protecting nominal income and letting internal growth gradually erase the difference instead of cutting pay outright.
How should harmonisation be done?
Proper harmonisation has four steps: evaluate and grade every role against one common set of criteria; build the new wage scale and pay table under Labour Code 45/2019/QH14 and publish it at the workplace as required; negotiate and sign contract appendices with each employee whose terms change; and communicate the catch-up roadmap to groups still below the band. Skipping individual negotiation is the error that makes the whole new system look unilaterally imposed.
How will staff react?
Negative reactions flare when staff hear the news through rumours before any official announcement, or when the higher-paid group is asked to take a cut with no explanation of criteria. Mitigation means publishing principles and criteria before numbers, protecting nominal income for existing staff, and opening a formal dialogue channel for questions. In practice a pledge that nobody loses nominal pay because of the merger buys more organisational stability than it costs.
How long does it take?
A realistic roadmap runs twelve to twenty-four months: the first quarter for job evaluation and a common scale, the next two quarters for negotiation, appendices and lifting the underpaid group, and the remaining period for annual increases to bring both groups onto one band. Deals with wide gaps or many job families should allow longer, and the transition cost belongs in the valuation model from the start.
Bottom line for buyers
Post-merger pay harmonisation succeeds when the employer respects the agreement-based limits of labour law, protects nominal income for existing staff and runs a single common scale for the future. Every shortcut through unilateral cuts returns as disputes, waves of resignations or administrative fines.