app\models\Invoice::updateBalances PHP Method

    public function updateBalances($balanceAdjustment, $partial = 0)
    {
        if ($this->is_deleted) {
            return;
        }
        $this->balance = $this->balance + $balanceAdjustment;
        if ($this->partial > 0) {
            $this->partial = $partial;
        }
        $this->save();
    }