Worked on the invopop/gobl repository to address a date inclusivity issue in tax rate calculations, ensuring that the 'Since' date is now correctly included in date comparisons. This backend development effort involved updating Go code to align tax logic with business rules, reducing the risk of incorrect tax rate application across edge cases. To reinforce reliability, a comprehensive suite of tests was added, expanding coverage to validate tax behavior across various date ranges. By focusing on both bug resolution and robust testing, the work strengthened continuous integration confidence and provided regression protection, demonstrating a methodical approach to backend quality assurance using Go.