How do I get a payment file my bank accepts?

Margin starts you with bank file templates for HDFC and ICICI bulk payments. For another bank, or when yours changes its layout, open Bank file templates (at the top of Daily → Payments, or under Settings on the finance pages) and click New template. Give it a name, the format (CSV or XLSX) and the number of header rows, then list the columns in the order your bank's file wants them, such as beneficiary name, account number, IFSC, amount and reference. A payment run's Generate bank file then offers it.