Build cloud accountancy SaaS for Amazon + eBay sellers

Build a cloud SaaS for Amazon and eBay sellers. Real double-entry ledger (GL, CoA, trial balance, P&L, Balance Sheet, Cash Flow), AR/AP sub-ledgers, period close into Retained Earnings, tax control ledger (output vs input tax). Amazon SP-API and eBay REST as separate pipes for orders, fees, refunds. Match marketplace payouts to bank deposits. Inventory and COGS per product line. Open Banking (Plaid / TrueLayer / Yodlee) plus CSV fallback. VAT/sales tax by buyer location and fulfillment channel. AI OCR for invoices (vendor, date, amount, lines) with human confirm. Smart categorization and a small AI accounting assistant. Web SaaS, responsive UI. AES-256 at rest, TLS 1.3 in transit, SOC 2-ready multi-tenant isolation. Thousands of orders per seller per month. Payroll. We own the code and the cloud account. Fixed price. Expert only. Answer the questions in the post. Our budget is open and you guys are open to bid.