COUNTIFS and excluding duplicates

I'm trying to come up with a formula which will count the number of units in a building associated with a business via the invoices. Some units have more than one invoice from the business, but I only want to count it once.

From the attachment there are 2 invoices for the apartment from Leo's, I would only want to count it as 1. I have the COUNTIFS for the building, unit and business which would return 2. Is there a way to make it so it would only count the first listing. The data would not be sorted or filtered in anyway. I have created a column to combine the building and unit and am not opposed to helper columns.

Book2.xlsx

Thank you for your help

Formula:

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entered as an array using Control+Shift+Enter


I'm sure there has to be a shorter version out there.

I got this formula off the forum some time back (sorry I dont remember the original author to credit)...

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I knew it could be done, and in 99 less characters too!

You are all amazing!!! Thank you so much!