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The law when a collective bargaining agreement changes your contract

Last updated: 6 Jul 2021

A collective bargaining agreement is an agreement between an employer and a trade union. In a collective bargaining agreement, an employer can agree to terms and conditions of employment with the union in relation to employees who are covered by the agreement.

This a complicated area of the law, and this article covers the law specific to when a collective bargaining agreement can or cannot change the terms of your contract. If you need advice on another area of trade union law, for instance, whether a union can represent you, we recommend that you contact ACAS.

When can a collective agreement change your contract

Trade unions can agree contract changes for employees when:

  • it’s written in the employee’s contract that the trade union can agree changes (‘incorporated’ into the contract)
  • it’s not written in the employee’s contract but the employer normally agrees contract changes with the trade union (an ‘implied’ term of the contract)

If this is done correctly, the changes agreed between the union and the employer are automatically binding and the employee will need to follow the new conditions whether or not they agree to the change. By contrast, an employee can object to a change of contract proposed by the employer that has not been agreed to in a collective agreement.

My contract doesn’t refer to a collective agreement. Is the change still binding?

It does not necessarily need to be written into your contract for your union to be able to negotiate contract changes on your behalf. Trade unions can agree contract changes for employees when it’s an ‘implied term’ of the contract that your employer normally agrees contract changes with a trade union.

Implied terms may be those that are agreed orally, or those that are made through ‘custom and practice’. Was it agreed orally that your union could negotiate this change on your behalf? Does your employer normally agree to contract changes with your union? Have they agreed to changes to your contract in the past?

This is a complicated area of law, and if you want to challenge a contract change on this basis, we recommend that you seek specialist advice. As a starting point, you could speak to ACAS.

I am not a member of the union. Can they still change my contract?

An employee doesn’t have to be a member of a trade union to agree changes for them, as long as the collective agreement says that the trade union can agree to the change and this is incorporated into your contract (either written in or implied).

When is a change by collective agreement unlawful?

Just because your union has agreed to the change in a collective agreement doesn’t mean that the change is lawful. There are case law examples where changes have been introduced by employers with union backing (or where the union has pushed for the change), and the change has later been found to be unlawful or discriminatory.

One of the most common situations where a change introduced by collective agreement is unlawful is if the collective agreement is not properly incorporated into your contract, either in writing or implied. This is a complicated area of law, and if you want to challenge a contract change on this basis, we recommend that you seek specialist advice. As a starting point, you could speak to ACAS.

Changes agreed through collective agreement are also subject to the Equality Act 2010. This means that the change must not be discriminatory on the basis of one of the protected characteristics. If the change disadvantages an individual or a group of people with a protected characteristic and there is no legitimate business justification for it, then the change in question may be indirectly discriminatory.

Some of the most common discrimination issues that come up for working parents are described below.

Indirect sex discrimination

If you are a woman and the change has an adverse impact on you because of childcare responsibilities, you may have a claim for indirect sex discrimination. This is because women still tend to bear the primary responsibility of childcare.

The courts recognise this dynamic, and it is called the ‘childcare disparity’. For instance, it has been successfully argued that, because women tend to have more childcare responsibilities than men, insisting that women work long or inflexible hours can be indirect sex discrimination.

In law, indirect sex discrimination occurs when:

  • Your employer requires something of, or imposes a working practice on male and female employees, for example full-time working or shift working, which puts women at a particular disadvantage compared to men (e.g., because of they bear the main burden of caring responsibilities).
  • You suffer a disadvantage as a result of not being able to meet the requirement or practice. This may be the difficulty of combining the required work hours with your caring responsibilities.
  • The requirement or practice cannot be justified by your employer as genuinely necessary for the business. Assessing this means the tribunal will examine how badly you are disadvantaged by the requirement.

Unfortuantely, men cannot claim indirect sex discrimination, but they may claim sex discrimination if they are treated less favourably because of their sex or gender. An example would be if an employer turns down an employee’s request for leave because they believe men shouldn’t have childcare responsibilties.

What should you do if a collective agreement changes your contract?

If your contract is changed by a collective agreement, and you do not agree with the change, you can consider taking the following steps.

Talk to your employer and the union

Discuss the change with your employer and the union. Explain how it will affect you, other options you could look at and what could happen if you cannot reach an agreement.

In broad terms, the role of a trade union is to work with the employer to agree changes which are in the employees’ interests. If you feel that a change imposed under the terms of a collective agreement doesn’t work in your interests (for example, because the newly imposed change of hours doesn’t accommodate your childcare responsibilities):

  • explain that you oppose the change of hours; and
  • explain why (for example, detail the effect that the change would have on your childcare arrangements).

This might trigger the employer and/or the union to reconsider the change, especially if they did not know the change might be problematic for you (and possibly other employees).

It’s always best to try to resolve things with your employer and the union first, before starting formal processes. It could be that the employer is willing to agree to maintain the existing working arrangement with you, to help to accommodate your childcare responsibilities.

Work under protest

If you are prepared to continue to work but disagree with the change, you should tell your employer and state in writing that you’re working ‘under protest’ until the problem is resolved. This shows that you have not agreed but you are prepared to try and work things out with your employer.

You should object without delay as soon as you know about the change. If you carry on working as normal without telling your employer you don’t agree, it may be taken as evidence that you have agreed to the change. There may be some allowance where you try the new working arrangements and then protest once you realise the impact will be so adverse that you cannot accept it.

Your letter should state that you are working under protest and your objection to the change. This template Letter of Protest may help you. You may then continue to negotiate with your employer and the union to seek to resolve the issue.

Raise a grievance

If the discussions with your employer don’t resolve the issue, or you think your employer has treated you very unfairly and the relationship is breaking down, you can consider raising a grievance

Raising a grievance is important if you think you might later raise a claim in the Employment Tribunal because failure to follow internal resolution methods can disadvantage your claim. 

It is often advisable to try and resolve things amicably, as formal processes can damage your relationship with your employer. For legal insight into grievances and tips on how to engage with your employer before it reaches this point, see our article on how grievances do more harm than good.

Make a claim in the Employment Tribunal

If you cannot come to an agreement, if your employer dismisses you or you feel forced to resign, you can consider a claim against your employer in the Employment Tribunal.

Note: These cases are very complex, so it is very important that you seek specialist legal advice and support, starting with ACAS.

If you want to submit an Employment Tribunal claim, there is a strict time limitation to do so – you must bring a claim within three months less a day of the date your change occurred or the date of the acts complained of (for discrimination).

In order to start the process of making a claim, you must first contact ACAS to start early conciliation. For further details of the process for bringing an Employment Tribunal claim please see our articles on starting a claim.


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The information on the law contained on this site is provided free of charge and does not, and is not intended to, amount to legal advice to any person on a specific case or matter. If you are not a solicitor, you are advised to obtain specific legal advice about your case or matter and not to rely solely on this information. Law and guidance is changing regularly in this area.