invoiceninja/app/Models/TaxRate.php

<?php
/**
 * Invoice Ninja (https://invoiceninja.com)
 *
 * @link https://github.com/invoiceninja/invoiceninja source repository
 *
 * @copyright Copyright (c) 2019. Invoice Ninja LLC (https://invoiceninja.com)
 *
 * @license https://opensource.org/licenses/AAL
 */

namespace App\Models;

use App\Utils\Traits\MakesHash;
use Illuminate\Database\Eloquent\Model;

class TaxRate extends BaseModel
{
    use MakesHash;
    
    protected $fillable = [
		'name',
        'rate'
	];

    protected $appends = ['tax_rate_id'];

    public function getRouteKeyName()
    {
        return 'tax_rate_id';
    }

    public function getTaxRateIdAttribute()
    {
        return $this->encodePrimaryKey($this->id);
    }

}