Sr Mainframe Developer (Core Banking / Accounting Systems)

About The Role
We are adding new composite reservoir accounts to our existing mainframe accounting platform: a pooled account structure in which balances from multiple subsidiary accounts are concentrated into, and drawn back from, a single reservoir account under defined sweep and allocation rules.
This is additional function inside a legacy system. You will read a large body of COBOL that has been in production for an extended period, much of it lightly documented, and extend it so that the new account type posts, settles, accrues, reports, and reconciles exactly as the existing types do. Correctness and traceability of every cent matter more than speed of delivery.
What You Will Do

• Analyze the current account master, posting, and balance-maintenance programs to establish where composite reservoir accounts must be recognized, and document what you find.
• Design and code the new account type end to end: master file and table structures, account opening and closing, participant linkage, sweep and reverse-sweep logic, allocation and interest apportionment, and closing balance derivation.
• Modify batch COBOL programs and JCL and extend the nightly and month-end cycles to include the new processing without lengthening the batch window beyond agreed limits.
• Add new CRAs to the audit trail, exception reporting, and reconciliation controls the new function requires, working with accounting stakeholders on what must be evidenced.
• Produce test data, unit and regression test packs, and parallel-run comparisons against current production output; investigate every difference until it is explained.
• Support implementation, conversion of any in-scope existing accounts, and early life production runs, including on-call cover during the first cycles.
• Leave behind program documentation, data-flow notes, and runbook updates that the support team can work from.

Required Skills

• 5+ years of Enterprise COBOL development experience in a z/OS environment
• 5+ Years of Experience with NaturalOne
• 3+ years of JCL development and production support experience
• 3+ years of experience with financial/accounting systems development or support including double-entry posting, balance/accrual maintenance, value dating, reconciliation, and month-end closeouts in a regulated environment
• 3+ years of experience working with Adabas and VSAM
• 3+ years of experience with tracing undocumented logic through copybooks, call chains, and job streams

Preferred Skills

• Experience with cash management, account pooling, sweeps, or treasury applications
• Experience with CA-7 scheduling and batch operations
• Experience with REXX, Python, or Java