This question has always existed but has been exacerbated by the travel restrictions and anxiety brought on by Covid-19.
The law is actually very straightforward. If you have a residence or ‘lives with’ Court Order than you can usually take your child out of the country for up to 28 days without needing extra permission as long as there is nothing in the Order to contradict this.
If you don’t have a Court Order, then you either need the permission of the other parent or a Specific Issue Order from the court which can often be obtained on a short-notice basis.
Ultimately, if parents cannot agree the court will decide based on what would be in the child’s best interests. The court will be guided by the welfare checklist and will consider where the holiday is to, what risks (if any) are present and what information has been provided by each parent.
If you anticipate a difficulty, you should take specialist professional advice as early as possible as court delays mean that you need to allow time for a decision to be made and don’t want to risk losing that holiday if it has already been booked!