A new powerful API for ZoneSoft invoicing system

Profile picture of Anabela Carvalho, Product Owner at Zone Soft

somoscuatro developed the integration of TicketBAI for Zone Soft’s invoicing system. Thanks to their efforts, the Zone Soft API now meets the technical and legal requirements of the tax authorities of the Basque Country. We found somoscuatro to be a trustworthy, professional, and reliable partner. We highly recommend working with them.

Anabela Carvalho

Product Owner at Zone Soft


Zone Soft




Retail Solutions

What we did

Custom API Development, Consulting, Maintenance Plan


2022 + Ongoing Maintenance Plan

The problem

Zone Soft wanted to enter the Basque Country market with its retail PoS and invoicing solutions. In order to do so, they needed to integrate their products with the Basque Government’s electronic invoice system, TicketBAI.

Our approach

As is often the case with public administrations, it was not always easy to obtain the complete technical requirements and documentation. As an additional complexity, the different provinces had slightly but significant differences in the way they wanted to receive data. This required us to do a lot of preparation, consulting TicketBAI technical team and legal departments.

We needed to investigate reliable and maintainable solutions for signing the invoice using the XAdES standard. Additionally, we looked for flexible template systems to generate invoices that meet the varying requirements of each retailer type served by Zone Soft.

The natural conclusion was to suggest creating a centralised API where all Zone Soft’s different services and products could send data to generate electronically-signed invoices.

The solution

After evaluating various technologies, we concluded that the most practical approach would be to develop the API using Slim, a lightweight PHP framework specifically designed for API development.

We ensured to follow the highest standards in terms of code quality. This included applying SOLID principles, making the code modular and extensible, and implementing automated quality and security checks such as sniffers and linters.

As invoice templates can be complex and vary greatly across the different provinces, we made the decision to use Twig to ensure future extensibility and long-term maintainability.

We put extra effort into the code that manages the digital certificate entity, handles Twig to XML conversion, and applies XAdES signatures.

The impact

Zone Soft successfully began selling their services in the Basque Country market being sure to comply with the legal requirements.

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