When you are happy that the bugs you reported in the warranty period have been addressed, you will need to give the supplier permission to invoice you. Try to distinguish genuine bugs from inconsistencies in the specification or other problems at your end. Your supplier should try to ensure that the final system is workable, but you should have had opportunity during the build to provide some guidance.

If you are working on this process then we will be delighted to assist you at any stage to the level that you require.