Senior Software Engineer I

• Design, build, and evolve core modules for tax filing and compliance, taking ownership from solution design through long-term maintainability.

• Use modern engineering practices, including AI-assisted development tools where appropriate, to improve productivity, quality, and maintainability.

• Develop and improve back-end and front-end components, APIs, interfaces, and integrations for a scalable, stable platform with large data volumes and complex tax logic.

• Contribute to new features and innovations, such as integrations with external systems and tools for tax advisory workflows.

• Work closely with domain experts and product owners to translate regulations and customer needs into reliable software solutions.

• Improve engineering quality through testing, refactoring, code reviews, and mentoring other engineers., Nextens ontwikkelt het toonaangevende platform voor fiscale software en compliance in Nederland. Duizenden belastingadviseurs en financiële professionals vertrouwen dagelijks op onze oplossingen om te voldoen aan wet- en regelgeving, efficiënter te werken en zorgeloos aangifte te doen.

Onze software ondersteunt jaarlijks meer dan 1 miljoen aangiftes en helpt organisaties omgaan met grote hoeveelheden data, complexe workflows en steeds veranderende fiscale regels. Dankzij onze diepe domeinkennis en voortdurende innovatie zijn wij een betrouwbare partner voor professionals die hun werk nauwkeurig, efficiënt en met vertrouwen willen doen.

Jouw rol

Als Senior Software Engineer bij Nextens neem je verantwoordelijkheid voor betekenisvolle onderdelen van een bedrijfskritisch platform dat dagelijks door duizenden professionals wordt gebruikt. Je ontwerpt en bouwt robuuste software, maakt doordachte technische keuzes en helpt de kwaliteit te verhogen van een platform waar nauwkeurigheid, betrouwbaarheid en onderhoudbaarheid echt tellen.

Je krijgt energie van complexe technische uitdagingen en weet kwaliteit, voortgang en onderhoudbaarheid goed in balans te brengen. Samen met domeinexperts, andere engineers en productowners vertaal je veranderende fiscale eisen naar software waar onze klanten blind op kunnen vertrouwen.

Je komt terecht in Team Fiscal, een product engineering team dat verantwoordelijk is voor belangrijke onderdelen van ons Nederlandse belastingaangifteplatform. Samen met fiscale experts en productcollega's vertaalt het team veranderende wet- en regelgeving naar betrouwbare software voor belastingprofessionals in heel Nederland.

Je werkzaamheden:

• Ontwerpen, bouwen en doorontwikkelen van core modules voor belastingaangifte en compliance, met eigenaarschap van oplossingontwerp tot langdurige onderhoudbaarheid.

• A bachelor's degree in Computer Science, Software Engineering, or equivalent experience.

• 4+ years of hands-on software development experience, with evidence of increasing technical ownership, preferably with C#, .NET, Azure, and modern web technologies.

• A strong quality mindset, including testing, refactoring, code reviews, clean architecture principles, and coaching others to raise engineering standards.

• Interest in using AI-assisted development tools responsibly as part of everyday engineering work.

• Strong analytical and problem-solving skills, especially when working with complex logic or data.

• A collaborative mindset - you enjoy working closely with engineers and domain experts to create practical, high-quality solutions.

• A focus on clean, maintainable code and a habit of writing tests to ensure quality.

• Fluency in English is required. You can read and understand Dutch requirements texts; spoken Dutch is helpful but not essential.

• Work-life balance * flexible hours, generous vacation days, and up to 20 days of remote work abroad per year.

• Competitive package * a strong salary, attractive benefits, and professional development opportunities.

• Great environment * a collaborative workplace, fully equipped in-house gym, and regular team-building activities.

Ready to Build What Matters? If you're eager to take ownership of complex engineering challenges and help shape how tax professionals work, we'd like to hear from you. Build software where precision matters and your expertise leads the way.

Nextens develops the leading tax and compliance platform for professionals in the Netherlands. Trusted by thousands of experts, our software supports more than 1 million filings each year and helps organizations navigate evolving tax rules, high-volume data, and complex workflows with precision and reliability. Built on deep domain expertise and a commitment to continuous innovation, Nextens not only ensures compliance, we set the standard for how tax professionals work. Your Role As a Senior Software Engineer at Nextens, you own meaningful parts of a business-critical platform used daily by thousands of professionals. You design and deliver robust software, make sound technical choices, and help raise the quality of a platform where accuracy, reliability, and maintainability truly matter. You enjoy complex engineering challenges and bring the judgement to balance quality, delivery, and long-term maintainability. Together with domain experts, fellow engineers, and product owners, you translate changing fiscal requirements into software our customers can trust completely. You will join Team Fiscal, a product engineering team responsible for key parts of our Dutch tax filing platform. Together with fiscal experts and product colleagues, the team translates changing legislation into reliable software for tax professionals across the Netherlands., At Nextens, your work powers the backbone of professional Dutch tax processing and helps thousands of professionals work smarter, faster, and more confidently. Our customers trust us not only for accuracy and compliance, but also because we innovate and improve how they work. What makes this role unique: * Technical challenges * scalable systems, evolving regulations, and high-volume data processing. * Real impact * your solutions directly support over 1 million filings every year. * Ownership * take responsibility for important platform areas and help guide technical choices. * Technical leadership * mentor colleagues and help raise engineering quality across the team. What we offer you