2. GENERAL INFORMATION ON TENDERING  2.1. Legal basis: what are the rules?  2.2. Rules on access to procurement: who may submit a tender?  The present Call for Tenders is governed by the Financial Regulation of the European  Chemicals Agency (ECHA), which refers to the provisions of  Regulation (EU, Euratom)  2018/1046 of the European Parliament and of the Council of 18 July 2018 on the financial  rules applicable to the general budget of the Union (the Financial Regulation) 2 .  The  Contracting authority  has chosen to award the contract resulting from this call for tenders  through an open procedure pursuant to Article 164(1) (a) of the Financial Regulation. In an  open procedure any interested economic operator (any natural or legal person who offers to  supply products, provide services or execute works) may submit a tender.  Participation in this call for tenders is open on equal terms to all natural and legal persons  coming within the scope of the Treaties, as well as to international organizations. It is also open to all natural and legal persons established in a third country which has a  special agreement with the European Union in the field of public procurement on the  conditions laid down in that agreement. This procedure is, however, not covered by the  Government Procurement Agreement (GPA).  The rules on access to procurement do not apply to subcontractors. Subcontracting may not  be used with the intent to circumvent the rules on access to procurement.  To enable  the Contracting authority  to verify the access, each tenderer must indicate its  country of establishment (and in case of joint tender – the country of establishment of  each group member) and must present the supporting evidence normally acceptable under  the law of that country/-ies. The same document(s) could be used to prove country/-ies of  establishment and the delegation(s) of the authorisation to sign as described in  Section  4.3 . Any economic operator willing to submit a tender for this call for tenders must be registered  in the Participant Register - an online register of organizations and natural persons  participating in European Commission's calls for tenders or proposals (participants). 10 2.3. Please be aware that following the entry into force of the EU-UK Withdrawal  Agreement on 1 February 2020 and in particular Articles 127(6), 137 and  138, the references to natural or legal persons residing or established in a  Member State of the European Union are to be understood as including natural or legal persons residing or established in the United Kingdom. UK  residents and entities are therefore eligible to participate under this call.  Registration in the Participant Register: why register?  2 Regulation (EU, Euratom) 2018/1046 of the European Parliament and of the Council of 18 July 2018 on the  financial rules applicable to the general budget of the Union, amending Regulations (EU) No 1296/2013, (EU) No  1301/2013, (EU) No 1303/2013, (EU) No 1304/2013, (EU) No 1309/2013, (EU) No 1316/2013, (EU) No  223/2014, (EU) No 283/2014, and Decision No 541/2014/EU and repealing Regulation (EU, Euratom) No  966/2012 (OJ L 193 of 30.07.2018, p.1).   For tenderers established in the United Kingdom: 