I want payslip only for one month not for more than month that's the reason I am consider to_date as a last date of month. But the problem is that when adding result=(contract.wage/payslip.day)*worked_days.Unpaid.number_of_days into the salary rule. gives me error "float division by zero" means payslip.day not contain 30 | 31. I dont understand why this happen. I am also tried your suggestion for one month payslip but not work.

Your payslip.day is zero, that's why. Properly update value to payslip.day

I don't know how you are updating payslip.day, but I can suggest you keep that as a computed field. I think you are updating the value wrongly.

Firstly i inherit hr.payslip with get_worked_day_lines method in that I have try this code

day_from = fields.Date.from_string(date_from)

day = calendar.monthrange(day_from.year, day_from.month)[1]

res1.append(day)

return res1[0]

I think I am inheriting wrong method that's the reason payslip.day

I think I am inheriting wrong method that's the reason payslip.day contain zero.

okay, make your field as computed and in the computed function, do the tweak

Thanks @Hilar AK for your time and suggestion. My problem is solved.