Hi bookkeeping-lmc
Thanks for your post, we're aware of and issue with this and we're tracking this on the following investigation - INV-61402 - CIS Suffered - unable to change the date for deduction calculation/save button unresponsive.
Our technicians are working to fix this and I've linked you to this so that you'll receive an email notification once the issue is resolved. In the meantime, please submit the figures manually via the HMRC site. 🙇:female_sign: