Free invoicing software in Bulgaria: what it must do

Bulgarian law does not require special, certified or NRA-registered invoicing software: tax documents may be issued manually or by automated means (Art. 112, para. 2 of the VAT Act). Free software, Word or Excel will do, provided the invoice has the required details, the numbering has no gaps, you meet the deadlines and you keep the documents. What sets the tools apart is how much of this they do for you.

Does the software have to be approved by the NRA

No. On its invoicing page the National Revenue Agency (NRA, НАП) states that "there is no prescribed invoice form": the invoice must contain the information under Art. 114, para. 1 of the VAT Act and may be on paper or in electronic form. The law provides for no registration, certification or list of invoicing software. The only software list the NRA keeps is for sales management software used at a place of business (SUPTO, СУПТО), which is something else.

The draft law on mandatory e-invoicing from 2028 does not introduce certification of invoicing software either. It provides for structured invoices to be issued through the NRA's system or through other software that reports the data in real time (draft Art. 112, para. 5 and Art. 120g, para. 1 of the VAT Act). The draft has not been adopted.

SUPTO and cash registers: when you need them

A fiscal receipt is issued for a sale at a place of business paid in cash, by card, by voucher or by another cash substitute (Art. 118, paras. 1 and 3 of the VAT Act). An invoice does not replace the fiscal receipt when one is required (Art. 118, para. 1). A place of business can also be an office or a home, if you sell from there (§ 1, item 41 of the supplementary provisions of the VAT Act), and a fiscal receipt is due when you are paid there in cash or by card.

When the client pays by bank transfer, no fiscal receipt is issued (Art. 3, para. 1 of Ordinance N-18 and Art. 9, para. 1 of the Personal Income Tax Act). A freelancer or small company that issues invoices and is paid into a bank account needs invoicing software only.

Some activities are exempt from cash registers altogether (Art. 4 of Ordinance N-18). For freelancers the key exemption is the liberal profession (item 8). Liberal professions are exercised by individuals such as consultants, translators, architects, engineers and chartered accountants, and by other individuals who work on their own account, are not sole traders and are self-insured (§ 1, item 29 of the supplementary provisions of the Personal Income Tax Act). They do not register their sales through a cash register even for cash payments, but they document the income they receive (Art. 9, para. 2 of the Personal Income Tax Act). The exemption does not apply to a company (EOOD, OOD) or a sole trader.

SUPTO is software for managing sales at a place of business where fiscal receipts are issued (§ 1, item 84 of the supplementary provisions of the VAT Act). Even there it is optional: the trader "may choose" software from the NRA's list, but once chosen, only that software may be used (Art. 118, para. 18). Card payments in an online shop have their own rules, described in Stripe and the Bulgarian invoice.

Word and Excel: legal, but risky

An invoice made in Word or Excel is legal if the content, numbering, deadline and storage rules are met. The risks are practical:

• Numbers are kept by hand. A skipped or repeated number is easy to make, and credit and debit notes must continue the same sequence.
• An issued file can be changed. Corrections and additions to invoices are not allowed: a wrong invoice is cancelled and a new one is issued (Art. 116, para. 1 of the VAT Act). Cancelled documents are kept too (Art. 78, para. 5 of the regulation implementing the VAT Act, ППЗДДС).
• Calculations are done by hand. The VAT base and the VAT are stated in euro, even when the invoice is in another currency (Art. 114, para. 5 of the VAT Act).
• There is no history. It is hard to prove which version of the file was sent to the client.

What free invoicing software should do

The first rows come from the law, the rest from practice.

The software does not replace a cash register where one is required: for payments in cash or by card at a place of business, unless your activity is exempt, for example as a liberal profession (Art. 4 of Ordinance N-18).

Numbering when you switch software

No provision covers switching software, but the numbering rules give the answer. The number increases with no duplicates or gaps (Art. 78, para. 2 of ППЗДДС) and does not restart with the new year (para. 3). So:

• 01continue from the number that follows the last invoice in the old software, or
• 02start a separate series that cannot overlap with the old one;
• 03do not issue from both tools in the same range;
• 04keep the documents from the old software for the whole retention period.

How to set the starting number in smetni.app is described in the Document numbering guide.

Storage: why you need to export your data

Invoices are kept for 10 years, counted from 1 January of the following year (Art. 12, para. 1, item 2 of the Accountancy Act). An invoice from September 2026 is kept at least until the end of 2036. The VAT Act requires tax documents to be kept in their original form until 5 years after the limitation period for the obligation they support expires (Art. 121, para. 1), and the longer of the two periods is the one that applies.

When you issue invoices with software, the data you create is kept electronically for the periods in Art. 38, para. 1 of the Tax and Social Insurance Procedure Code, whether or not you also keep it on paper (Art. 38, para. 3). So before choosing free software, check that you can download every document as a PDF, that you can export your data, and what happens to it if you change plan or close the account.

Electronic invoices: what the law requires today

A PDF invoice sent by email is an electronic invoice. It is allowed if the recipient accepts it, in writing or tacitly by processing or paying it (Art. 114, para. 9 of the VAT Act and Art. 78, para. 11 of ППЗДДС). An electronic invoice counts as issued when it is made available so that the client can receive it (Art. 113, para. 12).

You ensure the authenticity of origin, the integrity of content and the legibility of the invoice until the end of the retention period (Art. 114, para. 6). This is done through business controls that create a reliable audit trail between the invoice and the supply (para. 10). A qualified electronic signature is only one of the example methods (para. 11), so it is not mandatory. A signature and a stamp are not required invoice details either: see Bulgarian invoice requirements.

The deadline for issuing the invoice is 5 days from the tax event or from receiving an advance (Art. 113, para. 4). For a service completed on 30 September 2026, the invoice is issued by 5 October 2026.

What 2028 will change

The draft law published on 23 September 2026 provides that from 1 January 2028 VAT-registered suppliers issue structured electronic invoices to the EN 16931 standard, with an NRA compliance code. Under the draft, businesses not registered for VAT would issue them only to state and local authorities, but every taxable recipient would have to be able to receive them. If you are registered for VAT or close to the threshold, ask your software provider how it will handle the new invoices. The details and dates are in Mandatory e-invoicing in Bulgaria from 2028. Until the draft is adopted, it is not law.

Common mistakes

• "The software must be approved by the NRA." It need not be: the law allows manual and automated issuing (Art. 112, para. 2 of the VAT Act).
• "I need SUPTO to issue invoices." SUPTO is for sales with fiscal receipts at a place of business, and optional even there (Art. 118, para. 18 of the VAT Act).
• "As a freelancer I must buy a cash register." Not if you exercise a liberal profession as an individual (Art. 4, item 8 of Ordinance N-18) or your clients pay by bank transfer (Art. 3, para. 1).
• "Businesses not registered for VAT do not issue invoices." They do: the duty applies to every taxable person (Art. 113, para. 1 of the VAT Act), only without VAT.
• "Numbering starts from 1 every year." It does not (Art. 78, para. 3 of ППЗДДС), and notes continue the same sequence.
• "It is in the cloud, so I keep nothing." Keeping the records is your responsibility (Art. 38, para. 3 of the Tax and Social Insurance Procedure Code and Art. 121 of the VAT Act).

In smetni.app

In the smetni.app Sales module, invoices, quotes and notes are issued as PDFs, with gapless numbering in one or more series and a starting number you set yourself. Notes are linked to their invoice and continue the numbering of its series, and an issued invoice is cancelled, not edited. Export of documents to CSV and XLSX is on the Business plan and above.

You can also start on the free plan: up to 5 clients, invoices, quotes and notes as PDFs, and no card needed. It does not include sending by email or file uploads. You can move to a paid plan at any time from Settings.

All plans are on the pricing page, and the first steps are in the Your first invoice guide.