I cant input expense because of tax on my mobile

Welcome to the Community, adlanazhar.

Let me help and make you're able to enter your expense in QuickBooks Online.

You should be able to enter expense and add other line item for your tax. If not, we can perform some troubleshooting steps to fix it.

Sometimes, the app stores cache files that can cause an unusual behavior. In most cases, clearing the app's cache can resolve this issue.

For Andriod, here's how:

1. From the More Options ⋮, select Settings.
2. Tick Refresh Data, then choose Yes.

For IOS:

1. From the Menu ☰, select Help & Feedback.
2. Click Refresh Data, and then select Refresh.

You can also do it in your device settings. Here's how:

For Andriod:

1. Go to your device's Settings, select Apps (varies by device).
2. Choose QuickBooks app from the list, and then pick Storage.
3. Finally, hit clear data.

For IOS:

1. Go to your device's Settings, select Setting General iPhone Storage.
2. Choose an app that's taking up a lot of space.
3. To free up the storage without deleting the documents and data for the app, select the Offload App.

Once done, check if you can now enter your expense with the tax.

I'm adding this article for your reference in handling expense: Enter and manage expenses in QuickBooks Online.

Please don't hesitate to post your other concerns or leave a comment below for follow up questions about expense. I'll be around if you need help. Take care and have a good one!