What Client Says:

You didn't obtain approval from the human resources department.

How Client Pays:

This is a variation of the "preferred list" nonsense.

Usually there's something buried in a human resources policy manual that reads like:

All employment agencies and executive recruiters shall be referred to the human resources department for approval as to their fees, their qualifications, and the terms of hiring through them.

Supervisors who are serious about hiring are among the most pressured people in the place.  Management is screaming that work isn't getting done, other supervisors are complaining about bottlenecks, subordinates are threatening to quit from overwork, customers are angrily canceling orders, and overtime pay is pushing production costs through the roof.

Even if the supervisor knows about that policy, he doesn't care about it.  This is a matter of job security.  He's got a personal paycheck policy.

So he talks to you, approves the fee, interviews, and sometimes even hires without notifying the human resourcer.

When you confront the client, the supervisor "recalls" that he "told" you to obtain approval from HR, and that you "said" you did.  Will you be believed in court?  Possibly, if it's just your word against the supervisor's. 

It's not though, because:

1.  You have the burden of proof by a "preponderance of the evidence."  You're the plaintiff.

2.  The policy will be introduced into evidence to show the client's established procedure.

Your best evidence is a fee-confirming letter or e-mail to the supervisor that shows a copy being sent to HR.  It should include a sentence that reads:

If this does not confirm your understanding of our fee and terms, please reply immediately.

He is too busy to reply immediately.  The human resourcer won't either, since interfering with a hot hire is HR heresy.

It's so easy to collect when you know how to set up your five-figure fee!