RESKU is an very effective and user friendly android application for sales-officers.It has login screen for business purpose. By credential he will get his outlet stock information with credit for collection in future through three ways like cash, card and cheque. After login by multi-selection functional behavior he can select product for invoice. Every single category products has serial number. User can scan through bar code and its automatically calculate through its unit price, total, number of quantity after scan serial number. If user needs another product to add for invoicing there is an option to avoid complex way so that he doesn't need to go back stock list. Customer information gathering input field needs to fill so that company can inform him future promotion offer. By using resku user can collect money in different way like cash, cheque and card. After collection money outlet outstanding automatically reduced in background process REST API with asp.net c# and sql server 2008-2014.