non-payment for deployed application

[metzler]

I have been working as a consultant building an application for a customer.  At this point I have not received payment for the application (I do believe I will be paid), but this shows me a possible vulnerability - non-payment for programming services.  I know there are many ways to 'lock out' a built application after a certain amount of runs, or a length of time. 

I would hate to go the legal route and sue a company that I have provided services for.  

Does anyone use a certain method that they have found to help enforce payment, or at least prevent someone from using something that was built but never paid for?

[BertMcMahan]

This is one option: https://www.ni.com/en/support/downloads/tools-network/download.third-party-licensing-and-activation-...

(I haven't used it before, not sure what the costs/risks are)

[altenbach]

The Third-Party Licensing and Activation Toolkit includes an evaluation mode.

(Sorry, I am not familiar with it)

[CFER_STS]

The obvious solution is to obtain payment up front, or at least, establish some sort of deposit or installment arrangement according to particular milestones in a signed contract.  That said, obviously your client is not going to want to pay in full until they can verify that all requirements have been met, that the software isn't buggy, etc., and a reasonable operational interval is expected.  You can cripple the software after some period of time (via internal counter - not the system clock) unless an unlock code is entered, or you can tie the installation to a particular piece of hardware (dongle, etc.), you can make the software reliant on an internet connection that checks a server for authorization, or you can simply give them a version that times out and self-destructs after the evaluation period, and provide them the full version upon payment in full.  There's lots of options.

Of course, if you have already handed over un-crippled code, that's on you.  Call it a learning experience.  After some period of non-contact, I might be inclined to call them and ask why they've been silent, given that they probably want the version that has the randomly inserted calculation errors removed?...