Unpaid invoice

Hi all



I have been working for a company for the past 3 years on a self employed basis. I invoice them monthly and have always paid me on time.



Last Thursday I decided to no longer to no longer supply them labour as they were trying to change T&Cs of our arrangement.



I emailed them my invoice for the 1 week I had worked and asked them to remit within 7 days.

as today is the last dayIi have a feeling they are not going pay me for that week which comes to £900



What is my next move?



Are they allowed to wait a month like the previous invoices?



Thank you for any advice you can offer



Jamie

Unpaid invoice