Privacy policy
Which data we process, why, for how long and what your rights are. Version of 20 October 2026.
This is a translation for your convenience. Only the Polish text is binding.
1. Who is the data controller
The controller of the data described in this policy is Volt and Amaranth spółka z ograniczoną odpowiedzialnością, ul. 55 Pułku Piechoty 34, 64-100 Leszno, NIP 6972347881, KRS 0000733234 (we), which operates the Księguś service. For all matters relating to personal data, write to kontakt@twojksiegus.pl or by post to our registered office address. We have not appointed a data protection officer.
2. Two roles: your account data and your business’s data
- We are the controller of the data needed to maintain accounts, for billing and for the security of the service, and of the data of people who write to us or visit the website. This policy covers those data.
- We are a processor of the data that a business enters into Księguś or retrieves through it from the National e-Invoice System (KSeF) and the bank: invoices, counterparty data, bank transactions, employee data. Their controller is the business that uses Księguś. We process them only on its instructions, under the data processing agreement. If your data appear, for example, on an invoice or in the employee records of such a business, please contact that business first about those data.
3. What data, why and for how long
| Purpose | Data | Legal basis | How long |
|---|---|---|---|
| Creating and maintaining an account, logging in, messages from the service (e.g. address confirmation, notifications, reminders) | first name and surname, e-mail address, password hash, settings (language, appearance, notifications), roles in businesses, two-step login data | contract (Article 6(1)(b) GDPR) for the person who creates the account; our legitimate interest in serving the business that added you to its account (Article 6(1)(f) GDPR) | until the account is deleted; after that, only the label “Usunięty użytkownik” (Deleted user) remains in the business’s history |
| Business registration, trial period, subscription, pro forma invoices and VAT invoices | business name, NIP, address, first name, surname and e-mail of the person placing the order, payment history | contract (Article 6(1)(b)); tax and accounting obligations (Article 6(1)(c)) | for the duration of the contract, and billing documents for 5 years from the end of the tax year in which the tax liability arose |
| Security of accounts and the service (log of logins, failed attempts, exports and downloaded files) | IP address, time and type of event, account | legitimate interest: protecting accounts and data (Article 6(1)(f)) | 365 days |
| News and offers about Księguś sent by e-mail, only if you tick the consent box | first name, e-mail address, dates the consent was given and withdrawn | consent (Art. 6(1)(a) GDPR; consent to commercial information by electronic means under the Polish Electronic Communications Law) | until you withdraw consent (in account settings or via the link in the message) or delete the account; withdrawal does not affect the lawfulness of earlier mailings |
| Technical server logs (website and application) | IP address, address of the page visited, time, browser type | legitimate interest: operating and protecting the service (Article 6(1)(f)) | briefly; logs have a fixed size limit and are automatically overwritten |
| Website visit statistics (how many people, from where, on what device) | IP address cut to its network (last part removed), address of the page visited, time, browser and device type; from the address we work out, on our own server, the approximate country, voivodeship and city (DB-IP database, nothing is sent outside) | legitimate interest: knowing where visitors come from and developing the service (Article 6(1)(f)) | 35 days |
| Correspondence and support | e-mail address, content of the message and whatever you provide in it | legitimate interest: replying to the message (Article 6(1)(f)) | until the matter is resolved, and then until the limitation period for claims expires, if the matter may concern claims |
| Establishing, pursuing and defending claims | data from the above categories that are needed for this | legitimate interest (Article 6(1)(f)) | until the limitation period for claims expires |
Providing data is voluntary, but without an e-mail address, first name and surname, and business details it is not possible to create an account or conclude a contract.
4. Who we share data with
- Providers who process data on our behalf under data processing agreements: Hetzner Online GmbH (application server and database, data centre in Helsinki, Finland), OVH sp. z o.o. (encrypted backups, Warsaw, and the kontakt@twojksiegus.pl mailbox; sending SMS notifications: the phone number and the text of the message, only to people the company owner switched them on for, servers in the EU), Sendinblue SAS (Brevo) (sending e-mails from the service, servers in the EU).
- Public administration systems, when a business uses features that require this: the Ministry of Finance (Ministerstwo Finansów) (KSeF, white list of VAT taxpayers (wykaz podatników VAT)), Statistics Poland (Główny Urząd Statystyczny) (REGON register (rejestr REGON)), the Social Insurance Institution (Zakład Ubezpieczeń Społecznych) (e-ZLA sick notes, when the business fetches them). In that case we send what the feature needs, e.g. a counterparty’s NIP or an invoice.
- When a password is set and at sign-in we check in the Pwned Passwords database of Have I Been Pwned (Troy Hunt, Australia) whether the password has leaked from another site. We send only the first 5 characters of the password's SHA-1 hash, with no e-mail address or other data that could show whom it concerns. We never pass on the password itself.
- Persons or firms that keep our accounts, to the extent of billing documents.
- State authorities, when required by law.
We do not sell data or pass them to advertisers. Data do not leave the European Economic Area.
5. Cookies and browser storage
The twojksiegus.pl website does not use cookies or analytics tools from other companies (we count visits ourselves, from the server log, as described in section 3), and we serve fonts and scripts ourselves, without loading them from other companies.
The application (app.twojksiegus.pl) uses only cookies strictly necessary for it to work, so it does not ask for consent:
ksef_session: keeps you logged in and remembers the selected language; expires after 12 hours, and the session ends earlier after 60 minutes of inactivity;ksef_trusted: only if, during two-step login, you tick „Nie pytaj o kod na tym urządzeniu” (Don’t ask for a code on this device); valid for 30 days.
The application may also save copies of recently viewed pages in browser storage so that the “Back” button works faster. You can remove them by clearing the site data in your browser.
6. Your rights
You have the right to access your data, to have them rectified, erased, to restrict their processing and to data portability, and, for data processed on the basis of legitimate interest, also the right to object. In the application, on the Moje konto (My account) page, you can download your data and delete your account yourself. For other matters, e.g. if you want to correct your name or e-mail address, write to kontakt@twojksiegus.pl; we will reply within one month.
You may also lodge a complaint with the President of the Personal Data Protection Office (Prezes Urzędu Ochrony Danych Osobowych, Prezes UODO) (ul. Stawki 2, 00-193 Warszawa, uodo.gov.pl).
7. Automated decisions
We do not make decisions about anyone based solely on automated processing, and we do not carry out profiling. Automatic reading of invoices and matching of payments serve only to provide suggestions, which a human checks.
8. Security
The connection to the service is encrypted, and the most sensitive data are additionally encrypted in the database. Details are on the Security page.
9. Changes to this policy
When we change the way we process data, we will update this policy, and we will inform users of significant changes by e-mail.