Can someone confirm whether we can include a clause in our employment contracts that says any outstanding holiday entitlement must be used up during notice periods.

For example if staff give one month notice and have 5 days holiday remaining can we insist that they use up this entitlement during their notice period rather than us paying it to them when they leave?

and if so, can we enforce this if they are dismissed or made redundant?

Thanks.

SheikM