invoiceninja/app/Models/InvoiceItem.php

<?php namespace App\Models;

use Illuminate\Database\Eloquent\SoftDeletes;

/**
 * Class InvoiceItem
 */
class InvoiceItem extends EntityModel
{
    use SoftDeletes;
    /**
     * @var array
     */
    protected $dates = ['deleted_at'];

    /**
     * @var array
     */
    protected $fillable = [
        'tax_name1',
        'tax_rate1',
        'tax_name2',
        'tax_rate2',    
    ];

    /**
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function invoice()
    {
        return $this->belongsTo('App\Models\Invoice');
    }

    /**
     * @return mixed
     */
    public function user()
    {
        return $this->belongsTo('App\Models\User')->withTrashed();
    }

    /**
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function product()
    {
        return $this->belongsTo('App\Models\Product');
    }

    /**
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function account()
    {
        return $this->belongsTo('App\Models\Account');
    }

}