Smart Contract Developer - Core Banking

6-Month contract - Inside IR35 - up to £625 per day

London based - hybrid working - 3 days a week onsite

Role Overview

We are looking for an experienced Smart Contract Developer to join a major Core Banking transformation programme, supporting the implementation and evolution of a next-generation core banking platform based on Thought Machine Vault Core.

The successful candidate will work primarily within the Product Vault capability, designing, developing and maintaining Lending and Savings products implemented as Vault Smart Contracts. The role requires strong software engineering skills, experience working with complex financial products, and the ability to translate detailed business requirements into robust, testable and maintainable product logic.

The developer will work closely with Product Managers, Business Analysts, Solution Architects, QA Engineers and other engineering teams to deliver core banking capabilities across Lending and Savings.

Key Responsibilities

• Design, develop and maintain Thought Machine Vault Smart Contracts for Lending and Savings products and associated product features.


• Translate business and product requirements into scalable and maintainable Smart Contract implementations.


• Develop product logic covering areas such as:




• Interest calculation and accrual.


• Repayment and payment schedules.


• Fees and charges.


• Payment allocation.


• Account balances and balance dimensions.


• Product lifecycle events.


• Account amendments and servicing activities.




• Support the implementation and migration of Lending and Savings products onto the new core banking platform.


• Work closely with Business Analysts and Product Owners to clarify requirements, identify edge cases and define expected product behaviour.


• Collaborate with architecture and engineering teams to ensure Smart Contracts integrate correctly with surrounding services and platforms.


• Develop comprehensive automated tests covering product rules, scenarios, boundary conditions and regression behaviour.


• Participate in code reviews and contribute to development standards and engineering best practices.


• Investigate and resolve defects identified during functional, integration, migration and production testing.


• Support reconciliation and validation of financial calculations between legacy systems and Vault.


• Analyse existing product behaviour and legacy-system rules when supporting product migration.


• Contribute to technical design discussions and identify potential implementation risks or constraints.


• Support releases through development, testing, pre-production and production environments.


• Produce appropriate technical documentation describing Smart Contract behaviour and key implementation decisions.


• Work within established engineering governance, security and regulatory requirements.

Essential Skills and Experience

• Strong software development experience, ideally using Python.


• Hands-on experience developing Thought Machine Vault Smart Contracts.


• Good understanding of Vault Core, including concepts such as:




• Smart Contracts.


• Contracts API / Vault APIs.


• Posting instructions.


• Balances and dimensions.


• Scheduled events.


• Hooks.


• Interest accrual and application.


• Account lifecycle management.




• Strong experience developing and testing complex business logic.


• Good understanding of banking product concepts and financial calculations.


• Experience with automated testing and test-driven development.


• Strong analytical and problem-solving skills.


• Experience working with Git-based development workflows, CI/CD pipelines and modern software engineering practices.


• Ability to work effectively within multidisciplinary Agile delivery teams.


• Strong communication skills and the ability to discuss complex technical behaviour with both technical and non-technical stakeholders.

Highly Desirable

• Experience implementing Lending and/or Savings products.


• Experience migrating financial products from legacy core banking platforms onto Thought Machine Vault.


• Understanding of Lending and Savings concepts, including:




• Interest accrual and application.


• Repayment schedules.


• Fixed and variable interest rates.


• Fees and charges.


• Overpayments and underpayments.


• Deposits and withdrawals.


• Account maturity.


• Product and account closure.




• Experience working with financial event streams and downstream accounting or reporting systems.


• Knowledge of reconciliation between legacy and target banking platforms.


• Experience working within UK financial services or another highly regulated banking environment.


• Familiarity with microservices, event-driven architectures and cloud-native platforms.


• Experience working with Jira, Confluence and Agile/Scrum delivery practices.