How to Bid in Public Procurement Bulgaria 2026, CAIS Registration, Supplier Identifier, Documents & Timelines

Anyone planning to bid in public procurement in Bulgaria in 2026 must now navigate a revised registration process on the centralised CAIS (Centralised Automated Information System) electronic procurement platform, operated by the Public Procurement Agency (AOP). Since 1 April 2026, new rules require pre-bid CAIS registration and, for many award types, the issuance of a unique supplier identifier, a discrete compliance step that a significant number of bidders have not yet completed. This guide maps the entire procedure from account creation to bid submission, covering eligibility prerequisites, the qualified electronic signature requirement, required documents, realistic timelines, costs, and the specific changes introduced in 2026.

It is written for procurement managers, bid managers, infrastructure contractors and in-house counsel, including foreign bidders, who need a practical, step-by-step plan.

Overview of the Process and Who It Applies To

Bulgaria’s public procurement framework is governed by the Public Procurement Act (Закон за обществените поръчки / ZOP), as amended, and is administered by the Public Procurement Agency (AOP). All contracting authorities, central government bodies, municipalities, utilities and certain private-sector entities awarding publicly funded contracts, must publish notices and manage award procedures through the CAIS electronic public procurement portal.

For bidders (referred to in the legislation as “economic operators”), this means that participation in virtually any Bulgarian public tender now begins with a CAIS registration. The platform has two principal components: CAIS EOP (the electronic award platform at eop.bg) and CAIS EAP (the electronic appeals platform). Bidders interact primarily with CAIS EOP for locating tender notices, downloading procurement documents, submitting bids and communicating with contracting authorities.

The obligation to register applies to both above-threshold and below-threshold procedures. Above-threshold procurements (those exceeding the EU directive thresholds, published on Tenders Electronic Daily) have long required electronic submission through CAIS. The 2026 amendments extend the mandatory CAIS registration requirement and the supplier identifier obligation to a wider category of below-threshold procurement requirements. Foreign companies established outside Bulgaria may also register and bid, subject to additional documentary and translation steps described below.

Current tender notices are published in real time on the CAIS procurement register at app.eop.bg. The AOP’s English-language homepage provides guidance on platform navigation, user registration procedures and technical requirements.

Eligibility and Prerequisites for Bidding in Public Procurement in Bulgaria 2026

Before creating a CAIS account, every prospective bidder should confirm that it satisfies the eligibility requirements under the Public Procurement Act. The core tests are:

• Legal capacity. The bidder must be a legally constituted entity (or individual entrepreneur) with the capacity to enter binding contracts. For foreign companies, this is demonstrated by an equivalent certificate of incorporation or registration.
• Absence of exclusion grounds. The bidder must not be subject to mandatory exclusion grounds, including criminal convictions for fraud, corruption or money laundering affecting senior management; outstanding tax or social-security liabilities; or prior professional misconduct. Contracting authorities verify these through ex officio checks and the bidder’s own declarations.
• Company identification data. Bulgarian entities must hold a valid Unified Identification Code (ЕИК / EBN) from the Commercial Register. Sole proprietors use their personal identification number (ЕГН). Foreign entities that do not hold an EBN may be required to provide a local number of the foreigner (ЛНЧ / LNCh) for their authorised representative, or an equivalent national registration number, together with apostilled corporate documents.
• Supplier identifier. From 1 April 2026, bidders participating in certain award categories must hold a unique supplier identifier issued via the CAIS platform. This applies in particular to below-threshold procurement requirements where the contracting authority has specified the identifier as mandatory in the tender notice. Bidders should check the specific procurement notice to confirm whether the identifier is required.

Foreign Bidders, Practical Steps and Common Hurdles

Foreign companies registered outside Bulgaria may participate in Bulgarian public procurement on equal terms with domestic bidders. In practice, however, the following hurdles arise. All documents not in Bulgarian must be accompanied by a certified Bulgarian translation. Corporate registration extracts typically require an apostille (or consular legalisation for non-Hague Convention countries). The authorised representative who signs and submits the bid through CAIS will need a qualified electronic signature issued by a provider recognised in the EU or specifically accepted by the CAIS platform. Where the tender notice requires local registration or professional licensing (common in construction), the foreign bidder must demonstrate equivalence or obtain the relevant Bulgarian licence.

Early engagement with local counsel is strongly recommended to avoid disqualification at the evaluation stage.

Qualified Electronic Signature, How to Obtain and When to Use It

A qualified electronic signature (QES), known locally as КЕП, is mandatory for signing and submitting bids on CAIS EOP. The QES must comply with Regulation (EU) No 910/2014 (eIDAS) and be issued by an accredited trust service provider. Several Bulgarian PKI providers issue QES certificates; EU-based qualified certificates from providers listed on the EU Trusted List are also accepted. The certificate must be issued in the name of the individual who will sign the bid, and that individual’s identity must be linked to the CAIS user account. Bidders should allow adequate lead time: issuance can take 1–10 business days depending on the provider and the identity verification method (in-person, video identification or postal).

Once received, the QES must be tested on the CAIS platform before the bid submission deadline.

Step-by-Step Procedure, How to Bid in Public Procurement Bulgaria 2026

The following numbered steps describe the end-to-end process a bidder must follow to register, prepare and submit a compliant tender through CAIS. Each step is described in the order it should be completed.

Step 1, Create a CAIS Account (EOP/EAP)

1. Navigate to the CAIS EOP portal at eop.bg and select “Register” (Регистрация).
2. Choose the appropriate user type: “Economic Operator” for a bidding entity, or “Subcontractor / Third-Party Resource” if registering in a supporting capacity.
3. Enter the company’s Unified Identification Code (ЕИК) for Bulgarian entities. The system cross-references the Bulgarian Commercial Register automatically. Foreign entities enter their national registration number and upload supporting corporate documents.
4. Provide the contact details for the company administrator, this is the person who will manage the account, assign signing authority and receive system notifications.
5. Verify the account via the confirmation email sent by the platform. Until email verification is complete, the account remains inactive.
6. Link the company administrator’s qualified electronic signature to the account. This binding step is required before any bids can be signed or submitted.

Allow 1–5 business days for the full CAIS registration to be verified, depending on the speed of the Commercial Register cross-check and the complexity of any manually submitted foreign-entity documents.

Step 2, Obtain and Register a Qualified Electronic Signature (QES/КЕП)

1. Select an accredited PKI provider. Bulgarian providers include B-Trust, Evrotrust, InfoNotary and StampIT, among others. EU-wide qualified trust service providers listed on the EU Trusted List are also accepted.
2. Apply for a QES certificate in the name of the individual authorised to sign bids. Provide personal identification (passport, national ID) and, where the person is signing on behalf of a company, a power of attorney or corporate resolution.
3. Complete identity verification as required by the provider (in-person at a registration office, remote video identification, or postal ID verification).
4. Receive the QES certificate, typically delivered on a smart card, USB token or as a cloud-based mobile certificate.
5. Bind the QES to the CAIS EOP user account: log in, navigate to “Profile” → “Electronic Signatures”, upload or register the certificate, and perform a test signature.

Issuance typically takes 1–10 business days. Bidders participating for the first time should start this step at least three weeks before the expected tender submission deadline.

Step 3, Apply for a Supplier Identifier (If Required)

The supplier identifier is a new 2026 requirement. It functions as a unique registration number assigned to each economic operator within the CAIS system. The identifier is generated through the CAIS platform upon completion of a supplier registration application. The steps are:

1. Log in to CAIS EOP with an active account and bound QES.
2. Navigate to the “Supplier Profile” section and select “Apply for Supplier Identifier”.
3. Enter or confirm the company data (ЕИК/EBN, registered office, legal representative details, VAT number if registered).
4. Upload any supporting documents requested by the system (e.g., current Commercial Register extract, authorisation for representative).
5. Submit the application. The system assigns a supplier identifier upon validation, this may be instantaneous or may take 3–14 business days for manual review, depending on the entity type and the completeness of the submitted data.

Bidders should check the specific tender notice to confirm whether the supplier identifier is mandatory for that award. Industry observers expect the requirement to be extended to all CAIS-managed procedures over the course of 2026.

Step 4, Prepare and Upload Tender Documents in CAIS

1. Download the full procurement documentation from the tender notice page on app.eop.bg. Review all annexes, technical specifications, evaluation criteria and the specific instructions for the CAIS submission format.
2. Prepare the bid documents in the required format. CAIS generally requires signed PDF/A files. Each document that requires a signature must be electronically signed with the bound QES, not a scanned wet-ink signature unless the tender notice explicitly permits it.
3. Name files according to the naming convention specified in the tender notice (contracting authorities increasingly prescribe exact file-name formats).
4. Upload financial proposals, technical proposals, supporting certificates and the European Single Procurement Document (ESPD) into the designated sections within the CAIS tender submission form.
5. Where a bid bond or tender security is required, upload the bank guarantee or insurance instrument as a scanned and QES-signed document, or provide the instrument details in the prescribed CAIS field.

Pay careful attention to file-size limits. CAIS imposes maximum upload sizes per file and per submission. If a document exceeds the limit, the platform will reject the upload without saving a partial submission.

Step 5, Final Checks, Submit and Confirm Receipt

1. Review every uploaded file in the CAIS submission preview. Confirm that file names, signatures and document order match the tender notice requirements.
2. Verify that the QES-signed submission envelope is complete, CAIS will not permit submission if a required signature field is blank.
3. Click “Submit” before the tender deadline. CAIS operates on Bulgarian time (EET / UTC+2, or EEST / UTC+3 during summer). Submit at least 1–2 hours before the deadline to allow for any technical issues.
4. Save the CAIS-generated receipt of submission (the platform issues a timestamped confirmation). This receipt is the bidder’s proof that the bid was submitted on time.
5. Retain a full local copy of all submitted documents, the submission receipt and the QES certificate used, for the duration of the procurement procedure and any subsequent appeal period.

After submission, the bidder should monitor the CAIS inbox for clarification requests from the contracting authority and respond within the stipulated timeframes.

Procurement Timeline, Step Summary

Required Documents and Information, How to Bid in Public Procurement Bulgaria 2026

The documents needed for a compliant bid vary by procurement type and contracting authority requirements. The table below consolidates the documents most commonly required across commercial and construction tenders. Bidders should always cross-reference this list against the specific tender notice, which is the authoritative document for each procedure.

For construction tenders specifically, bidders should expect additional requirements: proof of registration in the Central Professional Register of Builders (ЦПРС), professional indemnity insurance certificates, and evidence of health-and-safety management systems. Always verify the exact list against the tender notice and any published clarifications.

Timeline and Key Deadlines

Timing is one of the most common failure points for bidders in Bulgarian public procurement. The procurement timeline involves both external deadlines set by the contracting authority and internal preparation lead times that the bidder must manage independently.

Key regulatory date: 1 April 2026, mandatory CAIS registration and supplier identifier requirements in effect for covered award categories.

The following countdown checklist provides a practical framework for managing internal deadlines relative to a known tender submission date:

After submission, bidders should be prepared for the evaluation phase, which typically lasts 3–20 business days depending on the complexity of the tender. If the contracting authority requests clarifications or supplementary documents, the bidder must respond within the timeframe specified in the request, usually 3–5 business days. Appeal deadlines for challenging award decisions are prescribed in the Public Procurement Act and run from the date of notification of the decision; these are strictly enforced.

Costs, Fees and Tax Considerations

Registering on CAIS itself is free of charge. However, several ancillary costs arise during the bid preparation process. The table below summarises the typical cost items. All amounts are approximate and should be verified directly with the relevant provider or authority.

Foreign suppliers should also consider VAT implications. Non-resident entities providing services or supplies to a Bulgarian contracting authority may need to register for Bulgarian VAT. The 2026 amendments to the VAT Act may affect registration thresholds and reverse-charge applicability. Bidders are advised to consult a Bulgarian tax adviser before submitting a bid that could trigger a local VAT registration obligation.

What Changes in 2026, New Obligations and Practical Impact

The amendments to the Public Procurement Act effective from 1 April 2026 introduce several changes that directly affect how to bid in public procurement in Bulgaria in 2026. The most consequential are:

• Mandatory CAIS registration for all award types. Prior to the 2026 amendments, certain below-threshold procurements could be conducted outside the CAIS platform. From 1 April 2026, all contracting authorities are required to manage procurement procedures through CAIS, and all bidders must hold an active CAIS EOP account to submit offers, including for below-threshold awards previously managed via simpler channels.
• Unique supplier identifier. A new supplier identifier system has been introduced within CAIS. The identifier functions as a persistent registration number tied to the economic operator’s profile, enabling contracting authorities to verify the bidder’s identity, past performance record and compliance status through a single reference. For tender notices published after 1 April 2026 that specify the identifier as mandatory, bidders without it will be unable to complete their submission in CAIS.
• Below-threshold procurement requirements tightened. The 2026 rules increase the documentation and publication requirements for below-threshold procurements. This includes mandatory ESPD submission, standardised evaluation protocols within CAIS and, in some cases, the supplier identifier requirement. Early indications suggest that contracting authorities are progressively adopting the identifier across all award categories.
• Legacy portal migration. Entities that previously accessed procurement notices through older AOP portals or municipal websites must now transition fully to the CAIS EOP platform. Legacy portal access has been discontinued for bid submission purposes. Bidders who have not yet migrated should create a CAIS account immediately and link their QES.

The likely practical effect of these changes is a short-term compliance squeeze: bidders who have not yet registered on CAIS or obtained a supplier identifier may be excluded from upcoming tenders simply for failing to complete a procedural step. Acting promptly eliminates this risk.

Common Pitfalls and How to Avoid Them

• Expired documents. Tax clearances and social-security certificates have limited validity periods. If the certificate expires before the tender submission deadline, the bid may be rejected. Fix: request fresh certificates with at least two weeks’ buffer and diarise expiry dates.
• Mismatched company names. The company name on the CAIS account must exactly match the name in the Commercial Register (or foreign equivalent). Discrepancies, including transliteration differences between Cyrillic and Latin characters, can trigger automatic rejection. Fix: verify the CAIS profile against the official registry extract before submitting.
• QES binding errors. The QES must be linked to the correct CAIS user account and the correct individual. If the QES is registered to a different person than the one who needs to sign, the submission will fail. Fix: perform a test signature on CAIS immediately after binding the QES.
• Late QES activation. Procuring a QES at the last minute leaves no recovery time if identity verification is delayed. Fix: begin the QES application at least three weeks before the first anticipated tender deadline.
• Wrong file formats. CAIS requires specific formats (typically PDF/A). Uploading standard PDF, DOCX or image files may result in rejection. Fix: convert all documents to PDF/A and verify file integrity before uploading.
• Missing supplier identifier. If the tender notice specifies the supplier identifier as mandatory and the bidder has not yet obtained one, CAIS will block submission. Fix: apply for the identifier as part of the initial CAIS setup, not when the tender deadline is imminent.
• Incorrect bid security format. Bid bonds that do not conform to the format specified in the tender notice (wrong currency, wrong beneficiary name, incorrect validity period) are a common ground for disqualification. Fix: cross-reference every element of the bid bond against the tender notice requirements before uploading.
• Missing the CAIS submission deadline. CAIS enforces deadlines to the second. A bid submitted even one second late will be automatically rejected, with no override available. Fix: submit at least 1–2 hours early and retain the timestamped CAIS receipt.

Sources

1. Public Procurement Agency (AOP), English Homepage
2. CAIS, Electronic Public Procurement Portal (EOP)
3. CAIS Procurement Register (app.eop.bg)
4. Ministry of Economy, Applying for Public Procurement (SME Guide)
5. Tenders Electronic Daily (TED), EU Notices and Threshold Reference