March 20, 2023


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  1. What is A-Cube?
    A-Cube Srl is an Italian company that is a pioneer and leader in the Italian market for e-invoicing. The company has been operating in the market since 2019, and in that time, their solutions have helped process over 20 million invoices in B2G communication. The company is expanding to new markets in the EU and everywhere where there is a need to implement e-invoicing
  1. What is A-Cube PL API?
    A-Cube PL API is software that allows for integration of any system with KSeF (National e-Invoicing System).
  2. What is REST API?
    REST (Representational State Transfer) is a type of software architecture and set of constraints that are usually applied to network services. A REST-API (Application Programming Interface) is a set of rules and protocols for building and interacting with network services that abide by the REST architectural style. In short, a REST-API allows a website or application to communicate with a server and request information from it or send information to it, using the HTTP protocol.
  3. What is KSeF?
    KSeF, or the National e-Invoicing System, is a central database of invoices. It is a computer system administered by the National Tax Administration that is used for issuing and receiving structured invoices. It has been operating since January 1, 2022 and is currently voluntary, but in the future it is supposed to be mandatory from 1st Jan 2024. The Ministry of Finance has announced that it has been approved by the European Commission. According to earlier announcements, the National e-Invoicing System is supposed to become mandatory on 1st Jan 2024, but there is no official announcement. For this reason, it is recommended to prepare for the obligation to use the system now.
  1. What is the difference between e-invoice and structured invoice?
    An electronic invoice is a document in electronic form issued and received in any electronic format. A structured invoice, on the other hand, is a new type of invoice that is issued using the National e-Invoicing System and has an assigned number identifying it in the system. A structured invoice is issued in accordance with a pattern specified in the regulations, using integrated software that works with KSeF and has a specific format for data, including all the elements required by the VAT act for invoices.
  2. Is structured invoice mandatory in Poland?
    Structured invoice is a new type of invoice that is allowed for use in economic transactions as of January 1, 2022. It was introduced as part of broader tax changes under the SLIM VAT 2 initiative, and as of January 1, 2024 it will be mandatory for all entities in Poland.
  3. Who is the ideal customer for your product?
    A-Cube API is an ideal solution for companies and organizations that want to streamline the process of electronic invoicing and exchanging digital documents with KSeF. Using our ready-made API, you can save valuable time and reduce project costs by eliminating the need to build and maintain a complex infrastructure in the cloud. Our solution will work in companies working on integrating systems with KSeF, platforms creating their own solutions, software houses building dedicated solutions for their clients, and even companies with complex and unique tools in which modifications are expensive or impossible. A-Cube API can be used as an extension of the entire infrastructure, making it a perfect choice also for auditing and accounting firms. 
    • The common denominator of the use of ACube PL API for the obtained value is:
      • ready-made API
      • reduction of time to create the entire solution
      • reduction of project costs
      • elimination of creating and maintaining complex infrastructure in the cloud use
    • Target customers for the application of the A-Cube PL API include.
      • Companies working on integrating systems with KSeF in a broad spectrum.
      • Platforms that develop their own solutions and automate processes related to the area of ​​accounting, costs, invoice monitoring, BI.
      • Software House building dedicated solutions for their clients.
      • Companies with complex and unique solutions where modifications are expensive or even impossible. In this case, ACube PL API can be an extension of the entire infrastructure
      • Audit companies
      •  Accounting companies
  1. Why is it beneficial to implement A-Cube PL API?
    The implementation of our solution will help save the time needed to build the entire project from scratch. By using A-Cube PL API, the costs of creating a programming team and scalable infrastructure will be reduced. Our product is ready to use and fills the gap between the customer’s system and KSeF.
  2. How long does it take to implement a solution from A-Cube?
    It depends on the complexity of the customer’s system. Full implementation requires 4 elements: Authentication, Invoices, Integration + Webhooks. In the case of our first early adopters, the implementation took a maximum of 7 days. Additionally, A-Cube has prepared detailed REST API documentation and ready-made SDKs that can be used in your own system.
  3. I have an accounting system, e-commerce or ERP in which the functionalities of sending invoices to KSeF are provided. Why do I need your solution?
    You probably already have your own accounting or even ERP system to handle your business, and the provider of these tools ensures integration with KSeF. Our solution can be used in parallel to existing systems or to extend them in the context of missing functionalities. Additionally, our API will be perfect for use anywhere where it is necessary to link several ideas, systems in a new product requiring invoice integration with KSeF.
  4. Does the API validate the invoice?
    Yes, when an invoice is received in XML or JSON format, A-Cube PL API checks its compliance with the government schema and if there is a validation error, it will be returned to the sending system. Such an invoice will not be sent to KSeF.
  5. Does A-Cube PL API support sales invoices?
    Yes. All invoices issued by your company are visible in KSeF and will be synchronized to your system from any date.
  6. Does A-Cube PL API support purchase invoices?
    Yes. All purchase invoices issued to your company are visible in KSeF and will be synchronized to your system from any date.
  7. Will KSeF send me a notification about a new invoice?
    No. KSeF does not have this functionality and it is unlikely to be implemented. In A-Cube PL API, we have built our own notification system for new invoices in KSeF. A-Cube PL API sends messages (so-called webhooks) with invoice information to your system to a properly configured URL address.
  8. Does KSeF allow you to send attachments?
    KSeF does not have the functionality to send attachments and it is unlikely that this feature will be implemented. In A-Cube PL API, we have built our own system for attaching files to invoices, allowing them to be sent along with the invoice. Attachments are stored in the A-Cube cloud and can be accessed by the recipient and sender of the invoice after a one-time authorization in the A-Cube system.
  9. Does KSeF include information about invoice payments?
    No. Such functionality may be implemented in the future. A-Cube has solutions in the field of Open Banking and it is possible to implement a solution that directly links invoices with payments from a bank account. Some of our partners already use their own extensions based on A-Cube PL API to insert additional information about, for example, payments or processing invoices in their own system.
  10. Will you be able to retrieve my old invoices?
    Yes. After registering in the A-Cube system and activating integration, the system will automatically start synchronizing invoices from the date of registration. It is possible to set a date earlier than which the invoices will be retrieved. The minimum date is 01.01.2022.
  11. Will I receive a UPO for invoices?
    Yes, but only for invoices sent to KSeF through A-Cube PL API. This is a technical limitation imposed by KSeF and it is not possible to obtain UPO using our API for invoices entered into KSeF in any other way.
  12. What programming languages ​​is the A-Cube PL API compatible with?
    A-Cube PL API is compatible with multiple programming languages such as PHP, as it is based on REST (Representational State Transfer) architecture, which allows communication between different systems via HTTP (Hypertext Transfer Protocol). The important thing is that the software adheres to specific rules and protocols, such as the use of HTTP methods (e.g. GET, POST, PUT, etc.) and data formatting in JSON format. This means that as long as the system meets these requirements, it can perform and respond to requests via API endpoints, regardless of the programming language it is written in. This allows for easy integration with various systems, regardless of their programming language or platform.
  1. Do you provide a tutorial on how to use your system for integration?
    Yes, we provide a tutorial on how to use our system for integration. We have API documentation and tutorials as well as ready-made components to aid in the integration process with KSeF.
    SDK: PHP +Other Languages (Contact us for more info)
  1. How many invoices can I manage with A-Cube?
    Regarding technical limitations at KSeF side, our system is able to handle 1.2mln per accountable and payable invoices for every NIP number per day. Our infrastructure is capable of handling large quantities and overloads, adjusting its resources when needed.

    Our infrastructure is capable of handling large volumes and overloads, adjusting its resources as needed. The KSeF. according to statements from the government’s side, able to handle up to 100 million invoices per day.
  2. What business cases can A-Cube PL API be used for?
    Ideal uses of our API include:
    • Tools requiring two-way communication with KSeF.
    • Older systems where it is not possible to implement a zero integration with KSeF or where it is not feasible due to costs or resource constraints.
    • Project management – API can be used as an extension of KSeF functionalities but also, allows for invoices to be integrated into existing processes such as approval or tagging with custom meta-data. This solution is already being implemented by our partners.
    • Business analytics – tools using invoice data for analysis and audits.