Add external links, to keep reference of other information related to a transaction. You can add more than one link to a transaction. 

There are two ways to insert links on transactions:

1. Click on the icon and insert your links:

2. Insert the link directly on the input field and record the transaction.

Open the transaction and click on the trash icon.

Click on the link icon on the transaction and it opens.

If you want to attach files, take a look here.