The ESPD (European Single Procurement Document) is a standardised self-declaration form that suppliers submit to confirm they meet a tender's eligibility and selection criteria. It lets bidders declare compliance up front instead of providing all supporting evidence at bid time.
Using the ESPD, a supplier states that it is not subject to exclusion grounds (such as unpaid taxes or serious misconduct) and that it meets the financial, technical, and professional requirements. Full evidence is usually only required from the winning bidder, which reduces paperwork for everyone else.
Two things are widely misunderstood about it. First, a self-declaration is still a legal statement: declaring compliance you cannot evidence is misrepresentation, and it surfaces at exactly the worst moment, after you have been named as the winner. Second, the reduced paperwork applies to the submission, not to your preparation, the certificates still need to exist and be current when you declare. Countries outside the EU use equivalent self-declaration forms under different names, so the underlying habit of keeping a standing evidence pack travels well.