Does "mark as paid" make any accounting entries? ie., does it impact any account whatsoever? OR, is it just for "tagging" a transaction as "paid" without any entries?

I think it affects the A/R account, assuming you are talking about customer invoices, but it also should affect A/P the same way

It will affect your reports if you file/report on a cash basis though

Hey Rustler. Thanks - but to your question: I'm referring to a vendor invoice. This is a vendor invoice (that has been paid previously), and I've already made the journal entries in Quickbooks. Thus, before I click "Mark as Paid," I just want to know what accounts would or wouldn't be hit, ie., so that it doesn't mess up the existing account balances. Thanks.