@niyas yes first I was giving category_id from code which are our xml files in data folder but now i'm manually creating the category_id in account.asset.category and referencing that category_id on basis of no. of Depreciations. here's my code

.py

@api.multi
def action_invoice_open(self):
    res = super(AccountInvoice, self).action_invoice_open()
    obj = self.env['account.asset.category'].search([('method_number', '=', self.total_months)], limit=1).id

    if self.deferred_revenue == True:
        self.env['account.asset.asset'].create({
            'name' : self.name or 'kkkkk',
            'category_id' : obj,
            'date' : self.date,
            'value' : self.amount_total,
            'partner_id' : self.partner_id.id,
            'invoice_id' : self.id,


        })
    return res

See the bold lines it all works fine if I don't comment those data files from manifest. but when i do i receive the error.

Hi,

From the code you might be creating some records/data in database models from data files, and you might not have supplied value for the required field during the process, that is why you are getting this message.

So check the records that you are creating from the code and supply the value for the field category_id

Thanks