I am suddenly unable to save an estimate I've been working on. A lot of work went into it now it's lost and can't seem to save once edited. Can anyone help please!

Welcome to the Community, bigwoodcc.

I understand the importance of creating and saving estimates in QuickBooks Online (QBO). For now, Let us do some troubleshooting steps if you are unable to save your estimate to determine if the issue is related to your browser. 

To begin, please open an incognito window. This will prevent your browsing history from being saved. You can use the following keyboard shortcuts based on the type of browser you are using:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Microsoft Edge: Ctrl + Shift + P
• Safari: Command + Shift + N

If the private browsing session works, you can clear the browser's cache to improve the program's performance. You can also use other supported, up-to-date browsers as an alternative which will provide the best and most secure experience with QuickBooks.

However, if the issue still persists after doing some troubleshooting steps. I suggest contacting support to help you further with your concern.

I will also add this article to help you personalize and add specific info to your sales form: Customize invoices, estimates, and sales receipts in QuickBooks Online.

Please feel free to drop a comment below, if you have further concerns about the estimate or other QBO-related concerns. I will answer them in any possible way.