What Makes a Reasonable Adjustment “Reasonable”? (UK Guide)
Most disputes about reasonable adjustments don’t hinge on whether support should exist. They hinge on one word: reasonable.
That word carries real legal weight. It protects disabled people from arbitrary refusals, and it protects employers from being expected to do the impossible. But it’s also where confusion creeps in, particularly when decisions are driven by instinct rather than evidence.
In UK law, reasonableness is not a vibe. It’s a test that has to stand up if challenged.
What makes an adjustment “reasonable”?
An adjustment is reasonable if it reduces or removes a substantial disadvantage at work and is practical in the context of the employer’s resources and operations.
This framework comes from the Equality Act 2010, which sets the legal duty to make reasonable adjustments
https://www.legislation.gov.uk/ukpga/2010/15/section/20
Importantly, employers are not required to agree to the exact adjustment requested. The duty is to remove the disadvantage, not to deliver a specific solution regardless of alternatives.
ACAS is explicit on this point and consistently stresses that many adjustments are simple changes to how work is organised, not expensive interventions:
https://www.acas.org.uk/reasonable-adjustments
The factors that determine reasonableness
When assessing whether an adjustment is reasonable, employers are expected to consider a small number of concrete factors.
These include:
whether the adjustment actually addresses the barrier
how practical it is to implement
the operational impact, not personal inconvenience
the cost relative to the organisation’s size and resources
whether funding or external support is available
whether an alternative adjustment would be equally effective
The Equality and Human Rights Commission frames this as a balancing exercise, not a free pass to refuse support:
https://www.equalityhumanrights.com/en/advice-and-guidance/reasonable-adjustments-disabled-people
When “no” can be reasonable
The vast majority of reasonable adjustments should be agreed. Many cost little or nothing and lead to better performance, retention, and morale.
That said, there are limited situations where an employer may lawfully refuse an adjustment. These situations are narrow and must be supported by evidence.
1) The adjustment does not reduce the disadvantage
If the proposed change does not address the actual barrier, an employer can refuse it and offer an alternative that does.
This is not a refusal of support. It’s a correction.
2) The adjustment creates a genuine safety risk
Health and safety can justify refusal, but only where the risk is specific, real, and cannot be reduced through another option.
Vague references to “risk” or “policy” are not enough.
3) The adjustment removes an essential part of the role
Employers are expected to adapt roles, but not to remove their fundamental purpose.
ACAS makes this distinction clear. Adjustments can change how work is done, but not eliminate core duties entirely:
https://www.acas.org.uk/reasonable-adjustments
4) The cost is genuinely disproportionate
Cost alone rarely justifies refusal. What matters is proportionality.
A small organisation may reasonably refuse an adjustment that a large employer would be expected to absorb. Employers should also consider whether Access to Work funding could cover or reduce the cost before relying on cost as a reason to refuse:
https://www.gov.uk/access-to-work
5) The request conflicts with legal or regulatory obligations
This is uncommon, but relevant in regulated environments where certain activities are legally restricted.
6) An equally effective alternative exists
An employer can lawfully refuse one request if they offer a different adjustment that removes the disadvantage just as effectively.
In practice, this is often the most robust outcome.
Reasons that are not reasonable
Some reasons sound intuitive in management conversations but do not hold up legally.
These are not lawful grounds for refusal:
“Others will want the same”
“We’ve never done this before”
“It wouldn’t be fair on the team”
“The manager doesn’t like it”
“This is really a performance issue”
“I don’t think they need it”
ACAS explicitly warns against decisions based on assumptions, discomfort, or cultural norms rather than evidence:
https://www.acas.org.uk/supporting-disabled-people/workplace-conversations-about-disability
Practical examples
Noise-cancelling headphones
Clear yes
A developer in an open-plan office struggles with background noise. A low-cost pair of headphones removes the barrier.
Outcome: Approve.
Discuss and adapt
A receptionist requests full noise cancellation but needs to hear phones and visitors.
Outcome: Adapt. Consider noise-dampening headphones or acoustic screens.
Lawful refusal
A warehouse operative requests headphones that would block safety alarms.
Outcome: Refuse on safety grounds and explore safer alternatives.
Permanent home working
Clear yes
A data analyst does location-independent work and the organisation already supports hybrid working.
Outcome: Approve.
Discuss and adapt
A team leader requests full remote work but supervises on-site staff.
Outcome: Explore hybrid arrangements.
Lawful refusal
A lab technician needs to work with physical samples.
Outcome: Refuse. The role is inherently on-site.
Removing essential duties
Clear yes
Rebalancing minor admin tasks with no material impact.
Outcome: Approve.
Discuss and adapt
A customer service worker asks to avoid calls entirely.
Outcome: Reduce call load and add support.
Lawful refusal
A driver asks to remove all driving.
Outcome: Refuse. Driving is the core of the role.
What makes a refusal defensible?
A defensible refusal shows that:
the disadvantage was clearly identified
the request was genuinely considered
evidence supports the decision
alternatives were explored
the aim remained to reduce the disadvantage
the reasoning would appear fair to an external observer
the decision is documented
A refusal without a written record is weak by default.
Handling the conversation well
For managers
Be transparent. Keep explanations factual. Avoid moralising about fairness. Offer alternatives and document the outcome.
For employees
Ask for the reasoning in writing. Request alternatives. Share relevant evidence if needed. Escalate only if the process itself breaks down.
The shared objective
A refusal is lawful only when it leads towards a better solution.
The Equality Act duty is not about granting every request. It is about ensuring the employee is not left at a substantial disadvantage.
Handled well, these conversations increase trust and clarity. Handled badly, they undermine both.
This is the gap Mosaic exists to close: turning judgement calls into a clear, consistent, recorded process that protects everyone involved.
Why TryMosaic exists
TryMosaic exists to remove guesswork from these decisions.
It gives organisations a structured way to:
identify the real disadvantage
record what was requested
document the reasoning behind decisions
explore and track alternatives
review adjustments as roles and needs change
Not to force every request through.
But to ensure every decision is defensible, fair, and focused on removing disadvantage.
Because the strongest position an employer can be in is not having said yes.
It’s being able to show that whatever decision was made, it was reasonable.
