Can we calculate Net Salary with openERp
Install hr_payroll module. Flow is as below:
Employee --> Contracts --> Salary Structure --> Salary Rules
In Contract, You can set Working Schedule for that employee with Wage. You need to configure Salary Structure with Salary Rules as per your need. Salary rules for Bonus, expenses, etc.
In that Salary structure, You need to add that rules. Now, go to the Employee Payslip menu, select that employee, Related information will be automatically come over there. Click on Compute sheet button. You will get Salary details in Salary Computation tab as per your Salary rules that you added in your Salary Structure.
For now, there is no link between attendance and payroll in OpenERP that you need to customize. It depends on requirements that how much time it will take for that! Hope this will help you.
In our company we decided to use openERP 
We now working to customize openERP with our work ... we can use it successfully in warehouse dept. and sallies  dept. 
My question is how to make openERP  calculate monthly Net Salary 
with deduct if the Employee absence or leave the work or if we decided to add bonus  
and if we can  programming new model and add it How this difficult to work and what about expected time  required to do 
OR how we can access to fields related with attendance and building our own program to calculate    Net Salary ?