Universal credit - Single to joint claim?

[SarCam463]

Hi,
I'm wondering if anyone has ever gone from a single to joint claim with their partners after them moving in.
He moved into my house, we have a child together and I have 2 from a previous relationship.
At the moment we are both out of work due to mental health reasons. I have LCW and he has LCWRA.
We have moved in together during both assessment periods, but it says there is a payment due on the 9th April (which is his usual payment date) would this be the last of the money he is entitled to before we claimed together on the 29th March?

Did you nominate that your ohs monthly assessment period continues moving forward or yours?

@choiceMummy I don't remember that being an option? It doesn't really say much on the journal apart from payment due the 9th April but can check how much it will be on the 5th.
I obviously have bills to pay this month and can't really afford to miss the payments, so I'm panicking a bit now.