It is matching old amounts (up to year old)with new invoices sometimes up to3 payments then not noticing new invoice amounts when paid turn up as uncatergorised income

I can share some insights about this, maddog-motorspor.

QuickBooks automatically downloads your transactions. Then it shows you if they match any records you’ve already entered in QuickBooks. Review each transaction one-by-one, then you'll have the option to match, add, view multiple matches. 

The uncategorized income is a default account and are used when it's unclear how transaction should be categorized. You can set up a bank rule, the Recognized tab. The purpose of banking rules is to accurately categorize transactions.

You can refer to this article to learn more about banking rules in QBO.

I'm always around whenever you need additional information.