Understand, Hanka, that you did not state that all the formalities for acceptance and checking for faults had been done, completed, when you asked about choice of tense. That being so, then you could write:
The materials will be returned after the company has confirmed that the work was accepted and that no defects were found. (the work was accepted and now the company will confirm its acceptance - the checking for faults and acceptance of the work is done, over, past.)
He will be deemed to be in default if he joined any firm, company or consortium although he had known that these entities provide/provded/had provided ??? services to EU customers.
The issue is, did the person join the company despite knowing they provided these services.
He will be deemed to be/as being in default if he joined any firm, company or consortium knowing that these entities provide (if they still do - else:) provided (they used to but no longer, but he joined while they were still doing so.)...
Hence, you may actually have to write:
He will be deemed to be/as being in default if he joined any firm, company or consortium knowing that these entities provide, or provided/did provide at the time of his employment, services to the EU.
Can you see that choosing the tense depends on knowledge of the whole circumstances? In the last part, for example, I am suggesting tenses when I do not really know what the regulations are surrounding this. So - does it matter if I did get a job with a firm that once did provide such services, but don't any more? Is this a "reminder" to people, or is this informing people of a new edict which has just come into operation? If the latter, then it doesn't apply to old employees and any use of past tense would be an error (since the nature of this law means it cannot be used retrospectively.)
Student or Learner