My cis deductions are not working through the app, it’s not calculating the cis amount on the invoices.It was working but has now stopped!

We acknowledge how important it is for you to efficiently handle the CIS deductions to your invoices, Benjjamin. Let's perform fixes on your app so that your CIS deductions go through seamlessly.
 

Unusual behavior in the QBO mobile app can occur when there is excessive data storage or uncleared cache. To resolve this, we'll reset the app data to refresh your device and set it to its default state. I'll guide you through the steps.

For IOS:
 

1. Go to Settings, then General.
2. Choose iPhone Storage, then tap the QuickBooks Online app.
3. Then click Offload App.
    

Please note that this will free up the storage without your app's documents and data.
 

For Android:
 

1. Go to Menu ☰, then click More Options ⋮.
2. Then choose Settings, then select Refresh Data.
3. Confirm by Tapping Yes.
    

Once done, you can restart your app by logging back into your account. 
 

If the issue persists, you can follow the suggested workaround in managing your CIS deductions by logging into your QuickBooks account through a web browser. 
 

Moreover, you may generate CIS  reports that contains details that will show on a Cash Basis following the HM Revenue and Customs (HMRC) guidelines.
 

Performing the provided troubleshooting steps above will determine if it is a mobile application issue. If you have more questions with managing your CIS deductions or other QuickBooks concerns, you can leave your reply below. We're here ready to provide further assistance for you.