Returns one expense transaction with its amounts, card, merchant, and full expense details: category, description, invoice number, accounting status, accounting fields (vendor, tax rate, payment account, expense account), and uploaded receipts.

The identifier can be either the card transaction ID (CTX-...) or its expense ID (EXP-...). Returns 404 if no matching transaction belongs to your business.

In expense.required_fields, true means that field is still missing. Each receipt includes an id you can pass to Delete expense receipt. expense is an empty object when the transaction has no expense.