I need to provide a simplified version of sales receipt: - uses a specific sequence code, stores in account.invoices - can be associated with a project - only one item, automatically selected according to the project, not changeable directly - customers list must be filtered by a specific tag/property

Should I develop a custom module? Or could I achieve this by working in OE UI directly, by working on a copy of Sales Receipt?

I'm working on OpenERP 7.0.x Thanks in advance