Holiday pay following dismissal

[Wilkarotin]

Posting on behalf of a family member. They have recently been sacked for gross misconduct (what that was I don't know for certain but have an idea - not theft). They were on a zero hour contract but have been getting the same regular shifts for approx 8 months. They worked there for 9 months.
They received their last pay into their bank this week and received less than a weeks wages (about a quarter).
They had never taken a holiday in the 9 months they worked there. They have spoken to their employer and they have said that they have sent a further cheque in the post which equates to 1.5 weeks wages.
I have done some Googling and am pretty sure I am right but wanted to check. I think that they are entitled to their accrued holidays pay (which I think works out to 16.2 days as they work 4 days a week for 9 months). This would then work out to their employer owing them 4 weeks wages, plus the last week they worked so 5 weeks in all, not the 1.75 weeks they have currently paid. Their employer stated via call that they are not entitled to accrued holiday due to being dismissed for gross misconduct.
Could anyone help? Am I missing anything?
Thanks in advance if you managed to read this, didn't realise it would be so long!

That clause has been in all my contracts yes. Hours worked only and suspension unpaid. You need to check the employment contract

No, a contract doesn't overrule the law.

www.gov.uk/holiday-entitlement-rights/taking-holiday-before-leaving-a-job#:~:text=Employers%20must%20pay%20for%20untaken,arrangements%20for%20the%20extra%20leave.

"Employers must pay for untaken statutory leave, even if the worker is dismissed for gross misconduct"

Oh, that's interesting, I've not been fired so I haven't had to challenge it. How about a use it or lose it by December 31st clause?

In Smith v Pimlico Plumbers Ltd, the Court of Appeal ruled that use it or lose it clauses can be legal provided:

• the employee has been given the opportunity to take paid leave
• they have been encouraged to do so, and
• they have been informed that they will lose the paid leave at the end of the leave year if they don't take it

An employer cannot simply rely on a "use it or lose it" clause. They must regularly remind employees of their entitlement and explain any deadlines clearly.

Depends why you couldn't use it