multa fixa + juro fixo diário

gistfile1.txt

{
    "amount": "300",
    "currency": "BRL",
    "on_behalf_of": "{{SELLER_ID}}",
    "customer": "{{BUYER_ID}}",
    "payment_type": "boleto",
    "payment_method": {
		"expiration_date": "{{BOLETO_EXPIRATION_DATE}}",
		"billing_instructions": {
			"late_fee": {
	        	"mode": "",
	            "start_date": "{{LATE_FEE_DATE}}",
	            "amount": 300
            },
            "interest": {
	        	"mode": "DAILY_AMOUNT",
	            "start_date": "{{INTEREST_DATE}}",
	            "amount": 500
            }
        }
    }
}