How can i have a serial number in all expenses vouchers

Hello there, imsolih.

Let me share some information about adding a serial number to expenses vouchers in QuickBooks Online.

QuickBooks doesn't have a specific field to add the serial number in the transaction. However, we can use the SKU field so you can have the serial number in all expenses. Note: we'll have to activate the SKU column from the Invoice page to make it visible to the expenses voucher. Let me show you how to do it. Here's how:

Enable the SKU column:

1. Go to the +New button.
2. Select Invoice under Customers.
3. Click the Gear icon. 
4. Then, tick the SKU box under Optional Columns.

When we create an item for this transaction, click the Product/Service drop-down arrow to add a new product. Then, enter the serial number from the SKU field. Then, hit the Save and Close button. Here are the sample screenshot for additional reference:

Also, I would suggest checking our blog website so you'll be updated with the latest releases features and review if a specific field to add a serial number in the expense voucher is included in the product updates. 

Let me know if you have other questions about QuickBooks. I'm always here to assists. Take care and have a good one!