For some reason I want to disagree with the general concensus here on getting the candidate involved.
This is between you and the company. (I refrain from using the world "client" so loosely in these situations.) Threatening them with turning them into a source company, badmouthing them, etc. is not going to get them to turn their ship around. There is no value (other than making yourself feel better for the moment) to any of that.
Informing the candidate will do nothing for your fee situation. The company will most certainly convince the candidate you are somehow at fault - and that will add no value. You will only look like a sore loser.
Very simply put - you have no leverage here. You've already provided the services. The candidate has accepted.
Send the invoice including all documentation. Follow up with them letting them know you expect to be paid. When/if they do not pay turn it over to a collections attorney who will work on contingency.
Take the high ground. Take the hit. Move on. (After sending the invoice.......)
As a last resort call Mike Biven or Stephen Schwartz
Mike is a Collection Rep for Coface Collections
We have used them in the past on occassion and they are very nice to deal with it when comes to getting paid. They do't harrass or threaten people and have always gotten me paid when I thought the account was lost. Granted we've only used them twice in 14 yrs but they did their job both times. Amazingly both clients respected the fact that we didn't send them to some pitbull agency and were very appologetic for not being able to pay their bill in a timely manner.
Not having a signed Agreement might be a wrinkle but if you have emails or faxes or anything saying that they wanted you to work the project then you might be able to collect.
Understand, this "New client" will most likely turn into a former client if you send them to collections but either way do you really want to do business with someone/ some company that doesn't value your contributions?
HTC Research Corp