Booking parental leave 9 months in advance...

I assume from the tone of the question that the employee is looking to book a full 4-week block of parental leave?

There's no particular requirement for a parental leave request to be "reasonable". In fact, this employee has given you considerably more than the 21 days required notice so it could be argued that they are being excessively reasonable. You can postpone the leave if there is a good ("significant") reason to, but with this much notice it would be hard to argue that any reason to delay cannot, itself, be delayed.

Why is this request for a statutory entitlement with a very good amount of notice presenting you such a challenge?

In most situations yes the more notice the better, in this case it means that it will 'block' the opportunity for others to book either annual leave or parental leave during that same period, as naturally clients have an expectation that there will be someone to service their needs, and therefore no further absence requests would be able to be considered. Was just interested in others thoughts.

Well, yes, but isn't that always the case? In a small team, every time someone books holiday, it "blocks" the opportunity for others to do the same. That's why you encourage people to book holiday well in advance so you don't have conflicting bookings at the last minute.

What makes this different is that it's parental leave rather than holiday and, again, I'm assuming it's for the maximum four weeks, which is probably more than you usually allow people to book holiday. But this isn't holiday. It's a statutory entitlement.

You can, of course, have a dialogue with the employee about this. But we walk a very dangerous path the moment we start to deny employees their statutory rights.

Well, yes, but isn't that always the case? In a small team, every time someone books holiday, it "blocks" the opportunity for others to do the same. That's why you encourage people to book holiday well in advance so you don't have conflicting bookings at the last minute.

What makes this different is that it's parental leave rather than holiday and, again, I'm assuming it's for the maximum four weeks, which is probably more than you usually allow people to book holiday. But this isn't holiday. It's a statutory entitlement.

You can, of course, have a dialogue with the employee about this. But we walk a very dangerous path the moment we start to deny employees their statutory rights.