CMS - dh wages have halved . What to do

[FlowerPower2525]

I'd like to start by saying dh has always paid his cms from day 1 never missed a payment.
However his wages / hours have halved. This is likely to be for around 1+ years. For many reasons all no fault of his own and illness. It's either less hours or no job.
I work however we've had to make large cut backs and unfortunately the cms payments are just too high on his wage currently. His ex won't be happy understandably however we also have to keep a roof over our dcs heads and also for when his dcs are here.
How does he go about changing the payment. I believe cms do calculations based on gross annual? Or can he call them with his new currently monthly salary.
Obviously if things change he will immediately up it again

He can call them and they will reassess it.

He just needs to ring them to report the change in income. It will be adjusted as it’s more than 25% change

Thank you. Wasn't sure if he had to wait until the annual assessment. He will call as soon as he has got his 1st wage slip shoeing less income.

He doesn’t need to wait for his first payslip. He must tell them now. His income has already dropped and they can’t backdate it.

If income changes by >25% the CMS changes from being based on last years tax return/P60 to a current year basis.