taxomate splits Amazon settlements into 2 different invoices (both in Xero and QuickBooks) to match the sales and the associated fees into their respective months.
Normally, Amazon settlements are paid every 1-2 weeks (15 days in most of the cases). This time period sometimes crosses the calendar month boundary.
Let's say an Amazon settlement is January 22nd to February 5th. Does this settlement belong in January or February?
Posting sales and fees in the month in which you have received your Amazon bank payment is not an ideal situation for reporting purposes. See Accrual vs. Cash Basis Accounting for more information.
taxomate provides the option to split the settlement and imports two different invoices to make sure to attribute the sales or fees to the month they actually occurred in. This allows for more accurate accounting and bookkeeping and to better forecast your growth. However, you can always change this setting in Settings > Invoice.