Can I use our existing sagepay with quickbooks?

Allow me to provide you some information about SagePay, alanpearce.

For now, we haven't received any updates yet about being able to link SagePay to QuickBooks Online (QBO). We are still waiting for them to reach out to our Developer's Team so both will work this out. This way, we can also provide an excellent product experience to do those who wanted to use SagePay with QBO. 

In addition, QuickBooks integrates with several third-party apps to cater to your business needs. You'll want to search and use the application that you think suits your needs in the meantime. 

For reference, consider getting product updates to stay current from this blog site: The QuickBooks Blog.

Fill me in if you have any concerns with QuickBooks integration. We're always right here to help you.