Hi there,
QuickBooks is designed to help reduce the amount of manual calculations required to make sure your books balance. I'll be happy to share more information so you can get started with reaping the benefits of QuickBooks Online.
Based on what you've described, it's vital I have a solid understanding on what you mean by making QuickBooks a default software. If you're using the QuickBooks Online Desktop app, I recommend checking with your operating system on your computer to see how you can make an app a default app. I'll also leave this question open in the community so other members that have experienced this can also chime in.
Converting from Sage 50 to QuickBooks can be a lengthy process but with the resources below, you'll have guidance on what to be aware of when converting:
You can also search for third-party migration apps on our site using this link here. I recommend choosing an app that meets your business need based on the app description and reviews.
In case you need further assistance, feel free to contact our support team using this link here. Otherwise, feel free to leave a comment below, I'll be on standby.