Terms of service

1. Parties and acceptance

These Terms of service (the “Terms”) are an agreement between Negative Epsilon SL, NIF B02850360, with registered office at Paseo de la Castellana 194, 28046 Madrid, Spain (“FiscalRail”, “we” or “us”), and the business or professional that creates or uses a FiscalRail account (“Client” or “you”).

You confirm that you act for business or professional purposes, have authority to bind the Client, and are not contracting as a consumer. You accept these Terms and the DPA by checking the acceptance box when creating an account, or by signing an order form that incorporates them. FiscalRail will not create an account through the dashboard unless that box is checked. If you lack authority or disagree, do not create or use an account.

2. Contract documents

The agreement consists of any signed order form, these Terms, the Data processing addendum (“DPA”), and product documentation expressly incorporated by reference. In case of conflict, a signed order form prevails, then the DPA for personal-data matters, then these Terms, then the documentation.

3. The service

FiscalRail provides invoice infrastructure through an API, dashboard and related tools. Depending on the selected tax regime and current documented capabilities, it may validate invoice inputs, assign invoice numbers, create immutable invoice records, generate documents, verify identifiers, send event webhooks and create or submit supported fiscal records.

Test accounts are for testing only. Their data and simulated authority responses are not production records and must not be treated as legally effective invoices, filings or validations.

We may improve or change the service. We will not materially remove paid core functionality during an active specifically agreed term without reasonable notice, except where needed for security, law, a public authority, or a third-party dependency.

4. Client responsibilities

The Client is the legal issuer of its invoices and remains responsible for:

• the accuracy, completeness and lawfulness of all account, customer, invoice, tax and payment data;
• choosing the correct tax regime, invoice type, tax treatment and correction flow;
• determining whether FiscalRail supports the Client's jurisdiction and transaction;
• reviewing issued documents and authority responses without undue delay;
• maintaining any certificates, powers, registrations, notices, consents and legal basis required for processing or submissions;
• retaining, exporting and using records as required by applicable accounting, tax and commercial law; and
• giving its users and integration providers appropriate instructions and permissions.

FiscalRail does not act as the seller, invoice recipient, tax adviser, accountant or general filing agent. Product rules and calculations are tools, not legal or tax advice. A successful API response does not prove that the underlying transaction or invoice is legally correct.

5. Accounts and security

You must provide accurate account information, keep email accounts, API keys and webhook secrets secure, apply least privilege, and promptly revoke compromised credentials. Actions performed with Client credentials are treated as Client actions unless caused by our breach.

You must promptly notify contact@negativeepsilon.com of suspected unauthorised access. We may require credential rotation or suspend affected access while protecting the service.

6. Acceptable use

You may not use FiscalRail to:

• break the law, evade tax, create deceptive records or infringe another person's rights;
• submit data you are not authorised to process;
• probe, disrupt, overload or bypass service security or rate limits;
• introduce malware or use the service to send unsolicited communications;
• resell or provide a competing hosted service unless we agree in writing; or
• reverse engineer the service except to the limited extent that applicable law cannot exclude that right.

We may investigate suspected abuse and suspend the minimum access reasonably necessary to protect the service, other clients or third parties.

7. Fees, balance and taxes

Current pay-per-use prices are shown on the website or in an order form. Prices are exclusive of VAT and other applicable taxes unless stated otherwise. We may change public prices prospectively by giving reasonable notice; a change does not reprice operations already completed.

Live accounts use a prepaid euro balance. Top-ups are non-transferable, may only purchase FiscalRail services and generally cannot be redeemed for cash. However, the Client may request a refund of the unused portion of a top-up within 15 calendar days after it is credited. The maximum refundable amount is the account's current positive balance; amounts already used, refunded, disputed or reversed are not refundable. After that period, unused balance is non-refundable except where we agree otherwise or applicable law requires a refund. If a payment is refunded, disputed or reversed, the corresponding amount is debited from the balance and may make it negative. Billable operations may be refused while the balance is zero or negative.

An operation is charged only according to the documented billable outcome. Network retries, rejected authority submissions and Test-account operations are charged only if the current pricing page expressly says so. Stripe processes card payments under its own terms and privacy information.

8. Immutability, corrections and authority services

Issued invoices, events, balance transactions and supported fiscal records are designed to be immutable. Corrections are made through linked credit notes, replacements, cancellations or other documented artifacts, not by editing history. You authorise us to preserve that history and to reject instructions that would compromise integrity or conflict with law.

When instructed through a supported feature, we may send data to tax authorities or official validation services, including the Spanish Tax Agency (AEAT) and the EU VAT Information Exchange System (VIES). Their availability, rules and responses are outside our control. We do not guarantee acceptance or a response time.

9. Client data and data protection

The Client retains its rights in data submitted to the service (“Client Data”). You grant us the limited rights required to host, copy, validate, transform, transmit and otherwise process Client Data to provide, secure and support FiscalRail, comply with law and follow your documented instructions.

For personal data in Client Data, the Client is normally the controller and Negative Epsilon SL the processor. The DPA applies. We act as an independent controller for account administration, billing, fraud prevention, service security and our own legal obligations as described in the Privacy policy.

You must not intentionally submit special-category data under GDPR Article 9 or criminal-offence data under Article 10 unless we expressly agree in writing.

10. Confidentiality

Each party will protect the other party's non-public business, technical and financial information using at least reasonable care and use it only for the agreement. This duty does not cover information that is public without breach, already lawfully known, independently developed, or lawfully received without restriction.

A party may disclose confidential information where legally required, after giving notice when lawful and reasonably assisting efforts to limit disclosure. This section does not reduce the DPA's obligations.

11. Intellectual property and feedback

We and our licensors retain all rights in FiscalRail, its software, documentation, models, designs and improvements. Subject to the agreement, we grant the Client a limited, non-exclusive, non-transferable right during the term to access and use the service for its internal business purposes and approved integrations.

If you provide feedback, we may use it without restriction or payment, provided we do not identify you publicly as its source without permission.

12. Third-party services

The service depends on hosting, storage, email, payment, authority and network providers. Our subprocessors for Client Data are listed on the Subprocessors page. Third-party services selected or connected by the Client, including webhook destinations, are the Client's responsibility.

13. Availability and support

Unless a signed order form says otherwise, FiscalRail is provided without a service-level agreement. Planned maintenance, urgent security work and dependency failures may interrupt service. We will use commercially reasonable efforts to operate and support it, but do not promise uninterrupted or error-free availability.

14. Suspension and termination

Either party may terminate an open-ended account by written notice. We may suspend or terminate access immediately where reasonably necessary for security, illegal use, material breach, risk to other clients or third parties, or a legal or authority requirement. For other remediable material breaches, we will normally give notice and a reasonable opportunity to cure.

The Client may close a Live account through the dashboard. Before closure, the Client must download any invoices, fiscal records, customers and other records it needs through the free API read operations. Closure is permanent: FiscalRail deletes the Live account, its Test account and Client Data and has no obligation to retain or restore those records for the Client. We retain only payment information needed for our own legal, tax and accounting obligations. Unused balance is forfeited on closure, so any refund covered by the 15-day guarantee must be requested first. Charges already incurred remain due. Provisions that by nature should survive—including payment, confidentiality, intellectual property, disclaimers, liability and governing law—survive termination.

15. Warranties and disclaimers

Each party warrants that it has authority to enter the agreement. We warrant that we will provide the service with reasonable skill and care.

To the maximum extent permitted by law, FiscalRail is otherwise provided “as is” and “as available”. We disclaim implied warranties of merchantability, fitness for a particular purpose, non-infringement, uninterrupted availability, and legal or tax outcome. Nothing excludes a warranty that cannot lawfully be excluded.

16. Indemnity

The Client will defend and indemnify Negative Epsilon SL against third-party claims, penalties, losses and reasonable costs arising from unlawful Client Data, the Client's underlying transactions or invoices, tax evasion or fraud, infringement caused by Client materials, or material breach of sections 4 or 6.

17. Limitation of liability

Neither party is liable for indirect, incidental, special or consequential loss, or loss of profit, revenue, goodwill or anticipated savings, arising from the agreement, to the extent permitted by law.

Each party's total aggregate liability arising from the agreement is limited to the amounts paid by the Client to FiscalRail during the 30 days before the event giving rise to liability. The cap does not apply to any liability that law cannot exclude or limit.

18. Changes to these Terms

We may update these Terms for legal, security, operational or product reasons. We will give reasonable advance notice of material adverse changes through the dashboard or account email. Continued Live use after the effective date constitutes acceptance where lawful. If you reject a material adverse change, your remedy is to stop using and terminate the service before it takes effect.

19. General

Neither party may assign the agreement without the other's consent, except to an affiliate or in connection with a merger, reorganisation or sale of substantially all relevant assets, provided the assignee accepts the agreement. The Client may not assign to our direct competitor without consent.

Neither party is liable for delay caused by events beyond reasonable control, except payment obligations. Notices to FiscalRail must be sent to contact@negativeepsilon.com; we may notify the Client through its account email or dashboard. Failure to enforce a provision is not a waiver. If a provision is unenforceable, it will be adjusted only as needed and the remainder continues. The agreement is the entire agreement on its subject matter and creates no partnership, agency or employment relationship.

20. Governing law and courts

Spanish law governs the agreement, excluding conflict-of-law rules. The courts of Madrid, Spain have exclusive jurisdiction, unless mandatory law requires otherwise.

21. Contact

Questions about these Terms may be sent to contact@negativeepsilon.com.