Im using the app on my phone but when im ready to save an invoice or estimate it say that there is an error and it doesn't let me save it. I need help.

Hello there, Rubenski. I'm here to help you fix the error when sending an invoice or estimate via the QuickBooks Online app.

May I know the specific error message you're seeing? So I can provide you with the appropriate resolution. 

To identify the cause of the error you're receiving, let's start by updating your app. We do this to clear stored app data. Here are the steps to follow: 

Android: 

1. From your device's Settings, select Apps (varies by device).
2. Choose the QuickBooks app from the list.
3. Select Storage. 
4. Tap clear data.

iOS:

1. From 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 Offload App.

If the issue persists, restart your device and reinstall the app from the Google Play Store.

Furthermore, log in to your QuickBooks Online account via a web browser and attempt to save the invoice from there. It will allow us to determine if the issue only happens to the mobile app. 

Here are the steps you can follow: 

1. Sign in to QuickBooks Online.
2. Enter your email address, user ID, and password or phone number.
3. Select Remember me. If you'd like to save your sign-in details.
4. Select Sign in.

If this works on the web browser, there's an issue with the mobile app. I'll let you contact our support team and report it. That way, they'll monitor and send you updates via email.

I'm adding these articles to help record the invoice payment: Learn how to create a new transaction from a receipt image. It provides detailed steps for a customer who wants to make a payment or has already paid you.

If you have any other concerns, you can always post them here. I'll be sure to answer them. Take care!