During the month, contributed to the laravel/cashier-stripe repository by addressing a critical invoicing bug related to tax calculations. Focused on backend development using PHP, the work involved updating logic in InvoiceLineItem.php to ensure unit amounts excluding tax are calculated accurately for both inclusive and exclusive tax scenarios. This solution incorporated comprehensive unit testing to validate the new tax-behavior logic and prevent future regressions. By refining the invoicing process, the changes improved tax compliance and reduced the risk of mischarges, ultimately decreasing potential support workload. The approach demonstrated attention to detail in backend logic and a commitment to robust, test-driven development.