Portugal: what the CCP lists
The authority excludes proposals that were submitted after the deadline, that do not include every required document, that do not follow the formalities for submission or that come from a bidder in one of the situations of art. 55 (CCP art. 70(2)(a), (c), (d), (j)). Those situations include insolvency, a recent conviction or professional sanction, and an unregularised tax or social security position, in Portugal or in the bidder's own State (art. 55(1)(a) to (e)).
Proposals are submitted on the electronic platform the authority uses (art. 62(1)) and, unless the tender documents allow otherwise, are written in Portuguese (art. 58(1)); the tender documents may allow another language for some of them (art. 58(2)). The winner must then provide the supporting documents on time; if it fails to through its own fault, the award lapses (art. 81(1), art. 86(2)). A guarantee, where required, is in general at most 5% of the contract price, or 10% if the winning price is abnormally low (art. 89(1) and (2)).
Spain: what the LCSP lists
People and companies in a prohibition to contract, such as a final conviction for certain offences, cannot contract with the public sector (LCSP art. 71(1)). Bidders declare their capacity and the absence of prohibitions in a responsible declaration (art. 140(1)(a)). The bidder with the best offer must put up a definitive guarantee of 5% of the final price excluding VAT, unless the authority waives it in the justified cases the article allows (art. 107(1)).
What follows
The earlier you see a contract notice, the more time you have for the paperwork that decides whether the offer is read at all. Keep certificates, declarations and signatory powers current before the deadline.