When importing transactions, the system will look up and match by Collector name and Merchant Number. If you have more than one deal with the same information it will apply to the earliest funded date not paid off. If all are paid off it will apply to the earliest funded deal.
If you can't seem to find the deal, the global search in the upper right corner will search deals by Merchant Number. Simply enter your merchant number and click search, a list of deals with that merchant number will appear.