Thank you Haresh. We don't want to install the expenses app because we don't use the hr app (which is a pre-requisite). Also we are using Odoo 10, Community Edition. We are looking for a method to keep track of expenses such as utilities, office supplies, vehicle mileage, advertising, insurance, etc. The only thing we could think of is to add these items as products that can be purchased (but not sold). The thing is, we may buy some items from ANY vendor we see when we're driving around, and so we need to enter the vendor in our vendor list. As far as mileage, what vendor can we enter for mileage? They are our personal vehicles. The business doesn't own them. We don't enter actual expenses. Instead we elect to use the mileage method of expense. We are looking for suggestions for either an app that facilitates this, or how to do it using our current configuration (Inventory Management, Sales, Invoicing, Accounting and Finance, Discuss, and Purchase Management.)

then only one option is custimisation to create new module

You answer that you don't want to implement the apps that will solve your requirement. So you are stuck.

You should also add accounting. The basic idea of any ERP system is to cover all your needs for the business. But yu must implement it...