
Marcy Calderon delivered six features across multiple HMRC repositories, focusing on API development, data mapping, and schema design using Scala, JSON, and CSV. In hmrc/property-business-api, Marcy implemented end-to-end migration flows for UK property business annual submissions, adding robust validation and error handling to improve data integrity and automate reporting. Within hmrc/individuals-capital-gains-income-api, Marcy clarified capital gains tax schema definitions and simplified API call paths by refactoring feature switch logic, reducing complexity and integration risk. The work demonstrated technical depth in backend development and functional programming, with careful attention to maintainability, auditability, and alignment with evolving business requirements.
April 2026 monthly summary for hmrc/individuals-capital-gains-income-api. Delivered a feature to simplify Capital Gains Tax API calls by removing conditional feature switch checks across URIs, improving downstream call paths, maintainability, and reducing future complexity.
April 2026 monthly summary for hmrc/individuals-capital-gains-income-api. Delivered a feature to simplify Capital Gains Tax API calls by removing conditional feature switch checks across URIs, improving downstream call paths, maintainability, and reducing future complexity.
March 2026 monthly summary for hmrc/individuals-capital-gains-income-api: Key focus on clarifying capital gains tax definitions within the API schema to improve data contracts and business clarity. Delivered Capital Gains Tax Definitions Clarification by updating schema descriptions to better reflect the purpose and context of tax allowances. This change reduces downstream interpretation errors, speeds integration with downstream services, and strengthens alignment with tax policy language. Commits associated: MTDSA-33438 Update descriptions (42061c72d3ceba7d2ab8f84e7503ac6bf88aa00d).
March 2026 monthly summary for hmrc/individuals-capital-gains-income-api: Key focus on clarifying capital gains tax definitions within the API schema to improve data contracts and business clarity. Delivered Capital Gains Tax Definitions Clarification by updating schema descriptions to better reflect the purpose and context of tax allowances. This change reduces downstream interpretation errors, speeds integration with downstream services, and strengthens alignment with tax policy language. Commits associated: MTDSA-33438 Update descriptions (42061c72d3ceba7d2ab8f84e7503ac6bf88aa00d).
January 2026 focused on delivering the HIP Migration API for UK Property Business Annual Submissions (Create and Amend) in hmrc/property-business-api. Implemented end-to-end migration flow with validation and robust error handling across multiple scenarios, enabling automated annual submissions and improving data integrity. This work reduces manual rework and supports regulatory reporting readiness.
January 2026 focused on delivering the HIP Migration API for UK Property Business Annual Submissions (Create and Amend) in hmrc/property-business-api. Implemented end-to-end migration flow with validation and robust error handling across multiple scenarios, enabling automated annual submissions and improving data integrity. This work reduces manual rework and supports regulatory reporting readiness.
December 2025 monthly summary for two repositories: hmrc/property-business-api and hmrc/individuals-capital-gains-income-api. Focused on delivering API enhancements, simplifying surfaces, and strengthening test coverage to boost reliability and speed of value delivery for downstream consumers.
December 2025 monthly summary for two repositories: hmrc/property-business-api and hmrc/individuals-capital-gains-income-api. Focused on delivering API enhancements, simplifying surfaces, and strengthening test coverage to boost reliability and speed of value delivery for downstream consumers.
Month: 2025-10. Focused on refining employment income data mapping to improve downstream data handling and reporting accuracy. Delivered a configuration change in the hmrc/income-tax-mtd-changelog repository that updates sa100_mapping_v2.csv to adjust the action for 'Individuals Employment Income' from 'Amend a Custom Employment' to 'Create and Amend Employment Financial Details'. This change is tracked under commit 3bcc5a618226629939c763e95c698be7b47933fb and lays groundwork for more precise categorization and downstream data routing.
Month: 2025-10. Focused on refining employment income data mapping to improve downstream data handling and reporting accuracy. Delivered a configuration change in the hmrc/income-tax-mtd-changelog repository that updates sa100_mapping_v2.csv to adjust the action for 'Individuals Employment Income' from 'Amend a Custom Employment' to 'Create and Amend Employment Financial Details'. This change is tracked under commit 3bcc5a618226629939c763e95c698be7b47933fb and lays groundwork for more precise categorization and downstream data routing.

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