Looks like HMRC have issued a change today.
The rules, also known as IR35, will now apply only to payments made for services provided on or after 6 April 2020. Previously, the rules would have applied to any payments made on or after 6 April 2020, regardless of when the services were carried out. It means organisations will only need to determine whether the rules apply for contracts they plan to continue beyond 6 April 2020, supporting businesses as they prepare.
I know a few people who planned to finish contracts a month early so there was no chance of receiving a payment after 6th April. Now it no longer matters - any work done before the 6th April is outside regardless of when the client pays you.