How can you determine discrimination for a denied rental application? Applicant has all criteria required ? What to do ?

As others have said difficult to determine if discrimination actually occurred without access to all facts. May simply be landlord choice due to their risk tolerance or other better qualified applicants (there may have been one or more other applicants who exceeded criteria and were a much better choice). Or other factors other than financial such as following up on applicant’s work and personal references etc.
If you do have substantiative reasons to believe your applicant suffered from discrimination, suggest you seek opinion from HAR’S legal counsel (Greg Harpold), or TREC’s legal helpline, who all may be able to determine if your applicant potentially has a case to pursue.

This is a difficult accusation to prove because housing discrimination can take many forms. However, HUD has provided us some guidance as a reference. Here are two of nine examples of housing discrimination according to the HUD website.
“Discrimination Isn’t Always Obvious – Example #1
John, who is a Black man, speaks to a prospective landlord on the phone about leasing an apartment. On the phone, the landlord seems eager to rent to John, but when John meets with the landlord in person to fill out an application, the landlord’s attitude is entirely different. A few days later, John receives a letter saying that his application was denied because of a negative reference from his current landlord. John is surprised because he never had problems with his landlord, and his landlord swears she was never contacted for a reference. John suspects that the real reason he was denied the apartment was because he is Black, so John files a complaint with HUD. HUD investigates and it turns out John is right – the landlord’s files show a pattern of discrimination because of race and color.
Discrimination Isn’t Always Obvious – Example #2
Jane is a Muslim woman who wears a hijab. Jane walks into the leasing office for a large apartment building because she saw a sign in the building’s window advertising several available units. Jane introduces herself to the leasing officer, who immediately says there are no units available. Jane asks to be put on the waiting list, but she never receives a call. Jane files a complaint with HUD because she suspects that the leasing officer does not want to rent to her because she is Muslim. HUD investigates and it turns out Jane is right –other employees of the building give HUD information that substantiates Jane’s claim of religious discrimination."
I am only allowed a certain number of characters in this post. You can refer to the source link to see the other examples provided by HUD. For all of your real estate needs contact 832-580-6535.

My wife and I own 7 rental properties. In our criteria, it states the applicant must have been at the same job for a year. If they were transferred by their company to Texas, I would consider that uninterrupted employment with the same company. If they moved from CA to TX in the exact same line of work for a better paying position, I may take them as long as I got a letter from their new employer AND I called in and talked to someone in the HR department. There are far too many scams out there these days so I look up the number for the company to get to the HR department. I never trust the number on the application.

The other thing on the rise is fake payroll checks since you can buy them on Craigslist. In the past month, I had a payroll check that didn't look quite right so I opened it in Acrobat Pro and went to "Edit Text & Images" and found that if I clicked on their name, I could move it and there was someone else's name underneath. The other one showed the company was banking with Wells Fargo California. My gut told me something was wrong so I finally Googled the routing number on the check and it belonged to Regions Bank. Be careful out there!

Make sure you gather and learn all the facts. I've seen falsified licenses, fake checks and brokers who take keys out of supra boxes before approvals. Do you know everything about this candidate....history, (criminal and rental), authenticity of docs, job, income. Maybe you can get a written referral from someone with clout for this client. If, like someone else suggested on this platform, that the agent is trying to get both sides of commission, then welcome to real estate. There's a lot of inauthenticity in this industry that is not policed by anyone.

Burden of Proof would be hard, Unless the Owner/Agent was openly discriminatory in-front of other about your specific client.
Just because someone meet the criteria doesn’t mean they will be approved for that property.

There isn't a way to determine discrimination when it comes to the denial of a rental application unless the landlord and/or listing agent actually communicates a discriminatory reasoning for denial. Despite a rental applicant meeting minimum requirements for a property does not guarantee acceptance. Especially if there was a stronger application they were competing with. I have also found, since COVID and with job loss on the rise, job security is something landlords are scrutinizing more. Perhaps a letter from the employer would help?

This is one of my pet peeves. Actually, it’s extremely likely that he or she just doesn’t want to split their commission with you. I’ve ran into this a few times, unfortunately and it’s hard to actually do anything. All you can do is submit a complaint to TREC. If that agent has multiple complaints, then maybe something will happen.

It will be very hard to prove. You will good and solid evidence.

Hard to tell you much without knowing all the facts. could one small email that is detrimental to the case

That would be extremely hard to prove. I think you would have to have evidence of a history of denials to that minority. Or someone that would testify of outspoken bias.

It’s difficult to know without knowing the full criteria beyond credit & employment. Of course you could have a client who meets everything that is required and they could still get denied over something as simple as another qualified applicant applied first. You could ask what specifically caused your client to get denied but proving discrimination would be difficult. Even if you believe it is, unfortunately without sure proof, there’s nothing much that can be done

What about their Credit???
Could be credit or rental issues. I would confirm.