Tandem Developer

Job Title: Tandem Developer
Location: London (2-3 days on-site)
Salary/Rate: Up to £450 per day (Inside IR35)
Start Date: 05/01/2026
Job Type: Contract (until 31/12/2026)

Company Introduction:

We have an exciting opportunity available with a leading organisation in the financial technology sector. They are currently seeking a skilled Tandem Developer to join their team on a long-term project.

Job Responsibilities/Objectives:

• In this role, you will be responsible for developing, maintaining, and optimising mission-critical applications within a high-availability environment, with a focus on cards and banking systems.
• Design, develop, and maintain applications on the HP NonStop (Tandem) platform.
• Work with TACL, Cobol, C, and Guardian for application development and support.
• Implement solutions for card transaction processing, settlement, and authorisation systems.
• Integrate applications with core banking systems, payment gateways, and compliance frameworks.
• Conduct system analysis, troubleshooting, and performance tuning for high-volume transactional environments.
• Provide L2/L3 production support for critical systems, ensuring minimal downtime.

Required Skills/Experience:

• The ideal candidate will have the following:
• Strong hands-on experience with HP NonStop (Tandem) systems.
• Proficiency in TACL, Cobol, C, Guardian, and Enscribe/NonStop SQL.
• Knowledge of ISO 8583 messaging, batch and online transaction processing.
• Experience within the cards domain (credit/debit card processing, EMV standards, tokenisation).
• Strong analytical and problem-solving skills.
• Experience working with fault-tolerant, high-availability architectures

Desirable Skills/Experience:

• Experience with modernisation strategies for Legacy Tandem applications.
• Exposure to Base24, Visa/Mastercard schemes, fraud prevention, and settlement processes.
• Banking or payments-related certifications or training.

If you are interested in this opportunity, please apply now with your updated CV in Microsoft Word/PDF format.

Disclaimer
Notwithstanding any guidelines given to level of experience sought, we will consider candidates from outside this range if they can demonstrate the necessary competencies.
Square One is acting as both an employment agency and an employment business, and is an equal opportunities recruitment business. Square One embraces diversity and will treat everyone equally. Please see our website for our full diversity statement.