Invoice numbering in Bulgaria: ten digits, series and gaps

A Bulgarian invoice number is sequential, has ten digits and contains only Arabic numerals, for example 0000000124 (Art. 114, para. 1, item 2 of the VAT Act, ЗДДС). Invoices, debit notes and credit notes share one ascending sequence with no duplicates or gaps, and numbering does not restart at the new year (Art. 78, paras. 2 and 3 of the regulation implementing the VAT Act, ППЗДДС). Sites may use separate ranges, and a cancelled document's number is never reused.

The rules for a Bulgarian invoice number

The rules for an invoice number sit in two acts: Art. 114, para. 1, item 2 of the VAT Act sets the format and Art. 78 of the regulation the sequence.

A кочан (literally a "book") is the Bulgarian word for a numbering series: once a paper book of forms with permanently printed numbers (Art. 78, para. 1, item 1 of the regulation), now a series with a starting number in the software. The other required contents are in Bulgarian invoice requirements under Art. 114.

Invoices and notes share one sequence

Invoices, debit notes and credit notes use the same sequence, because numbers under Art. 78, para. 2 of the regulation "do not depend on the type of form or document". A credit note takes the next free number, not 0000000001 in a separate sequence. With several series, practice is for the note to use the series of the invoice it corrects. When to issue a note is covered in credit and debit notes in Bulgaria.

Numbering at the new year

Numbering does not go back to 0000000001 on 1 January: it "does not depend on and is not broken by the end of the calendar year" (Art. 78, para. 3 of the regulation). If the last invoice of 2026 is No. 0000000980, the first one of 2027 is No. 0000000981. It starts again only when the possible numbers run out, after written notice to the regional office of the National Revenue Agency (НАП, the NRA) (Art. 78, para. 3).

Series and numbering by site

Each branch or site may issue from its own range of numbers (Art. 78, para. 4 of the regulation). The range is used up gradually, and when it is full a new one is set. Ranges should not overlap, because every number must identify the invoice uniquely (Art. 114, para. 1, item 2 of the VAT Act): for example, head office uses 0000000001-4999999999 and the Plovdiv site 5000000001-5999999999. Record the ranges in your accounting policy.

Under self-billing the customer issues the invoice on the supplier's behalf under a prior agreement between them (Art. 113, para. 11 of the VAT Act), numbered from a range the supplier provides (Art. 79a, para. 12 of the regulation) and marked "самофактуриране" (self-billing) with the legal basis (Art. 79a, para. 11).

When a document gets its number

Neither the VAT Act nor the regulation sets when a number is assigned, but the gapless sequence of Art. 78, para. 2 of the regulation in practice means it is given on issue. A numbered draft that is later deleted leaves a gap, while an issued document is never deleted: the issuer keeps cancelled documents (Art. 78, para. 5).

Who must follow ten-digit numbering

The ten-digit number is mandatory on every invoice under the VAT Act, including invoices from a business that is not VAT-registered. As a rule, every taxable person supplying goods or services issues invoices (Art. 113, para. 1 of the VAT Act), and Art. 114, para. 1, item 5 expressly provides for an unregistered supplier.

Art. 78 of the regulation is written for registered persons, but para. 13 exempts unregistered persons' forms only from the "original" mark and the VAT number (para. 1, items 2 and 4) and requires numbering to continue after deregistration. Practice is therefore for an unregistered business to number without gaps or resets too. The Accountancy Act (ЗСч) requires a number in Arabic numerals only on every primary document sent to an outside recipient (Art. 6, para. 1, item 1). The regulation has no express rule for numbering on VAT registration; the sequence usually continues. Confirm your case with your accountant.

An invoice from a supplier VAT-registered in another member state, for an intra-Community supply of goods or a service received, meets the requirements of Art. 114 of the VAT Act even when its number is not ten digits or contains other characters (Art. 78, para. 9 of the regulation).

Proformas and quotes are outside the sequence

A proforma invoice and a quote do not take a number from the invoice sequence, because they are not tax documents: the tax documents under the VAT Act are the invoice, the note to an invoice and the protocol (Art. 112, para. 1). A proforma with the next invoice number would leave a gap, so proformas and quotes get a separate sequence. When the customer pays against a proforma before delivery, the invoice for the advance is, as a general rule, issued within 5 days of payment (Art. 113, para. 4 of the VAT Act) with the next number in the sequence. See proforma invoices in Bulgaria.

Skipped, repeated or wrong number: what to do

Fix a numbering error so that every number stays tied to one document and the sequence can be explained.

Skipped number. A skipped number has no issued document: for example, 0000000124 is followed by 0000000126. The law does not say how to close such a gap, and practice varies: a document with that number, cancelled and kept by the issuer (Art. 78, para. 5 of the regulation), or an internal record of the reason, such as a software error. Choose the approach with your accountant.

Repeated number. The number must identify the invoice uniquely (Art. 114, para. 1, item 2 of the VAT Act), so in practice the later document is treated as wrongly compiled, cancelled and reissued (Art. 116, para. 1). If it is already in either party's ledgers, a protocol is also drawn up (Art. 116, para. 4), though it may be omitted when the cancelled and the new document carry the same date (Art. 81, para. 4 of the regulation). See cancelling an invoice in Bulgaria.

Switching software. If you issue from both tools for a while, each uses its own range. Record the number and date at which the old series closed, so its unused numbers are clearly not gaps. See also free invoicing software in Bulgaria.

Is there a fine for a numbering error

The VAT Act has no separate penalty for a skipped or repeated invoice number alone. Art. 182 penalises a registered person for a tax document not issued or not entered in the ledgers when, as a result, less tax is declared payable or more is claimed back: the penalty equals the tax, with a statutory minimum (para. 1), or 25% of the tax, also with a minimum, when the document is issued or entered in the following period (para. 2). Art. 185 concerns fiscal and system receipts under Art. 118, not invoices. The Accountancy Act has a general penalty for any unmet obligation under it (Art. 77, para. 1), which a number that is not made up only of Arabic numerals may fall under (Art. 6, para. 1, item 1 of the same Act). A gap is still a reason to check whether an invoice for the missing number was never issued.

Example: two sites, a credit note, a cancelled number and a software switch

A VAT-registered company has a shop in Sofia. Until 30 June 2026 it invoices from old software, the last invoice being No. 0000000412. From 1 July 2026 it uses new software and continues the same sequence; numbers 0000000414-0000000419 are issued between July and September. On 15 September 2026 it opens a site in Plovdiv with its own range from 5000000001.

Number 0000000421 stays taken and the cancelled invoice's copies are kept (Art. 78, para. 5 of the regulation). It and the new invoice carry the same date, so the protocol under Art. 116, para. 4 may be omitted (Art. 81, para. 4 of the regulation). The credit note continues the Sofia sequence; the Plovdiv series runs on its own.

A document cancelled in the month it was issued goes into the issuer's sales ledger without values and is not entered by the customer (annex 12 to the regulation), so its number stays visible. On 1 January 2027 both series carry on, for example with 0000000468 and 5000000031.

In smetni.app

In the Sales module, Bulgarian numbers have ten digits, are zero-padded and carry no prefix, and the counter never resets at the new year. You can have several series (кочани), for example one per site or shop. You set the starting number when you create a series, for example to continue from another tool, and it cannot be changed later. The number is assigned only on issue, never to a draft, and skips numbers held by imported documents, so no duplicate is produced. Notes take the next number from their invoice's series, and a cancelled invoice keeps its number. Series are on every plan; importing previously issued documents needs Pro or higher (plans and pricing). See Document numbering, Your first invoice and Organizations and documents.