br_boleto/sequence/payment_order_sequence.xml
<?xml version="1.0" encoding="UTF-8"?>
<odoo>
<record model="ir.sequence" id="payment_order_seq_id" >
<field name="name">Payment Order</field>
<field name="code">payment.order</field>
<field name="padding">4</field>
<field name="prefix">O.C. </field>
</record>
</odoo>