Hello Nikul,

You can add character function field with and store=True, which returns the string with percentage sign appends, like this :

@api.depends('basic')
def _compute_percent(self):
    for rec in self:
       rec.per_net_amt = str(rec.basic) + " %"

per_net_amt = fields.Char(compute='_compute_percent', string="percent field", store=True)
​basic = fields.Float("Basic Amount")

Hope it will help you.
Thanks