Thank You Ivan, i was searching for such a feature for loooooong days ! I'm gonna try to enhance your module to add some features, eg: show the Debt amount on the POS customer view. However, i don't understand how money is returned by customer to refund their "debt" ? Where are we supposed to do that ?

iMaugis, there is a module's description https://github.com/yelizariev/pos-addons/blob/master/tg_pos_debt_notebook/__openerp__.py#L10 : To make repayment of a debt create payment of another type (e.g., cash ). This payment should be more than total amount of current order (also, you can create empty order). After this click on debt button and validate. Now difference between payment and total is amount of returned money

Hum ... In fact i'm using this module => https://github.com/yelizariev/pos-addons/tree/master/pos_debt_notebook So instructions are not the same, and it seems that refunding debt doesn't work as expected.

Ok, i see, you already added this "Debt" field in the POS view :) The fact is i that when tg_pos_debt_notebook is installed, i got an error in the POS: TypeError: order is undefined http://192.168.1.19:8069/web/js/web.assets_backend/309c537:4520 I will investigate... Thank you again

These modules was tested on saas-5 version of odoo. With newer version there can be errors.

OK, i work on a local Debian machine with nightlies http://nightly.odoo.com/8.0/nightly/src/odoo_8.0.latest.tar.gz