Hi Jill 

Welcome to our Community.

I've found the reference and will get an answer for you (and others).

https://www.cipd.org/uk/knowledge/webinars/flexible-working-day-one-right/

The situation from April is :
An employee may not—
(a) make more than two applications under this section to the same employer during any period of 12 months;

If they have made a request in the preceding 12 months they can make another. If they want to make a third request they must wait until the first request is over 12 months old

Hi Jill 

Sorry this took a few days. Here is the response Tony Mulcahy - Assistant Director at BEIS - sent across.

When calculating the requests made within a 12 month period, any such request made within the 12 month period immediately before the request is made is to be counted, even if the request was made before 6 April 2024. Section 1(8) of the Employment Relations (Flexible Working) Act 2023 is clear that “On or after the coming into force of this section, in any determination of the number of applications made under section 80F of the Employment Rights Act 1996 by an employee during a period of 12 months, any such application made before that coming into force (and during that period) is to be included.”