aAdverse action if applicant didn't submit screening.

[Tanner Forster]

I use Tenantcloud for my rental propertys. 
I showed the property on Sunday. That night I had an applicant apply, I started screening them Monday.
Tuesday I heard back from their employer and sent them an acceptance letter, telling them I would take the property off the market and hold it for them till the first of the month as soon as I got their deposit to hold. They paid the deposit Wednesday morning. Tuesday night I had another applicant apply, they failed to have their co-applicant fill out an application even though it is required for everyone over 18, instead they just added their info in the notes section. They also didn't complete the screening information for the background/credit check so I never received that. 
I assume I should send them an Application Denial Adverse Action letter, though I don't think I need to because they didn't complete the background/credit check. Should I just state that I chose to go with another applicant? Want to cover my *** here but I'm not sure how far to go?

Thanks for any insight.