Python / Full-Stack Developer - HMRC Corporation Tax XML Gateway Integration (Sandbox Phase)

We are an established corporate operational entity, and we have been officially registered by the HMRC Software Developer Support Team (SDSTeam) as an approved software vendor. We require an experienced backend software engineer to build a secure, lightweight Python middleware engine that programmatically communicates with the HMRC Corporation Tax (CT) Online XML Test Service. Core Deliverables XML Payload Generation: Build a generation engine that takes structured corporate accounting variables (JSON format) and maps them dynamically into a compliant GovTalk XML structural envelope matching the official HMRC CT600 and FRS 105 Micro-entity schemas. Cryptographic IRmark Calculation: Implement the mandatory client-side cryptographic canonicalization (C14N) and hashing functions (SHA-256) to generate the required IRmark signature string, injecting it back into the payload before transmission. Gateway Communication Engine: Code the secure HTTPS connection loop to transmit the signed XML payload to the HMRC Third Party Validation Service (TPVS) / Test Gateway using our corporate Vendor ID and provided test credentials (Sender ID and Test UTR). Response Parsing & Error Logging: Parse incoming synchronous/asynchronous server responses from HMRC, automatically logging successful responses or extracting specific structural validation error codes for localized error handling. Technical Stack Preferences Python 3.x (with standard, secure libraries such as lxml, requests, and cryptography) Clean, modular, well-documented code blocks Strict environment variable/credential separation Documentation Provided Upon Hire The successful candidate will be granted immediate access to our secure HMRC sandbox authentication parameters, test passwords, and the official HMRC technical PDF packs (Basic guide for XML software developers / Corporation Tax online support specifications). All official government credentials and test keys are already fully provisioned.