Hi there, webmaster3.

Thank you for visiting the QuickBooks Community. I'll share some details and troubleshooting steps to ensure the amount that appears when sending the invoice reminder is accurate. 

When sending an invoice reminder to your customers, it gently informs them about their due dates or payment cutoff. That said, it only covers the open invoice and won't include the last paid invoice as part of the total due. To fix this, I suggest making sure to choose the correct invoice when sending a reminder.

Here's how:

1. Click the Sales menu on the left panel.
2. Choose the Invoice section.
3. Find the entry and open it to review the details and confirm if it's correct.

Additionally, you'll have to ensure that the previous invoice shows paid in the system. This is to make sure that this will not carry on the latest transaction so it will not appear when sending reminders. You can follow the steps below.

1. Click the Sales menu on the left panel.
2. Select the All Sales tab.
3. Look for the previous invoice and see if this is tagged as Paid.

If the issue persists, it could be the cache full of history, and temp files cause unexpected behaviors, such as the amount showing incorrectly when sending a reminder. I recommend logging in to your QuickBooks account using a private browser. Then, try to send a reminder invoice from there. This is to rule out the possibility of a webpage issue, and private browsing doesn't store local files or cache.

Use these keyboard shortcuts based on the browser you're using.

• For Firefox or Microsoft Edge, press Ctrl + Shift + P.
• For Chrome, press Ctrl + Shift + N.
• For Safari, hold down Command + Shift + N.

If it works in incognito, I recommend clearing the cache of your regular browser. This removes the history or log of sites so you can start with a clean slate. You can check this article to see the steps: Clear cache and cookies to fix issues when using QuickBooks Online.

If the steps above didn't work, use another supported browser as alternatives.

Lastly, you may open this article to see different details on how the Sales page gives you a great at-a-glance view of all your income/sales entries: View sales transactions.

Let me know if there's anything else you need help with on your invoice transactions. I'm always here to help you anytime. Take care and keep safe!