Is there a faster way to input multiple receivables? I'm looking for something that will allow me to input about 48 invoices with the same information only to different clients.

Is there an application in the A/R module similar to FAST! in the A/P module, or is entering each of these invoices individually my only option?

AR does not have a Fast! option as AP and SB do.  There are two options to quickly enter the information and avoid the manual process.  The first is to import the information.  This could be easy depending on how familiar you are with the process.  The other option, which I recommend, is to add the invoice to the first record and then select to add the invoice to a group of clients.  This will add the exact invoice to all records selected.  The only hitch is that you need to create a query for the clients to add the invoice to.  If it's random clients, make sure you mark the Preview clients before invoices are added checkbox on the Add Invoices to a Group screen.  This will allow you to unmark the clients you do not want to add the invoice to.  Take a look at Knowledgebase solution BB102857 for the steps.

Hope this helps!