What is the singular contract?
Well, the famous "singular contract" sounds like something mysterious, but in reality it is quite direct (although not as much as one would like). Basically, in the world of tenders and public contracts, this type of contract appears when there is something so specific or rare that it does not fit even in a typical contract. That is, you can't put it in the same bag as others because ... it simply does not fit.
And be careful, it is not just that there is a single supplier. It is rather that the contract brings under the arm such strange or particular conditions that neither of joke could group it with another. Example? It can vary from duration, rare payments, deliveries on Mars (well, not so much, but almost), or things that only that contract asks. It is like the "custom suit" of contracts.
This is used for everything a bit: buy unique things, hire services that no one else offers, to bring super specialized experts for a very specific topic. If you are a company and you want to get into tenders, understand this is key. Because, if you manage to prove that you and only you can meet those specific needs, the same and take the fat prize. But neither does you emotions: competition is usually fierce and sometimes the risks are higher, because conditions are not the usual.
Ah, and do not forget that this is governed by the laws of each country. That is, what is worth in Mexico does not necessarily apply in Spain or in Peru. You have to check local legislation not to put the leg.
Anyway, the singular contract is like that legal unicorn in public purchases: weird, difficult to see, but if you find it and understand it, you can get a lot of juice. If you are going to launch yourself for one, you better know what the thing is about, because the game can change you.