When entering expense transactions in QuickBooks, what date should I use (the date on the invoice, the date it posts to my business credit card, etc)? Thank you! Nicki

The date of the transaction is what we do here.  

Thanks for checking in with us, nickiblack95-gma.

The date on the top of the invoice should be the date the invoice was generated. The dates under the 'description' should be when the product was delivered or the service was performed. Also, you'll be the one to decide when you want to be paid and set the date in the Due Date field. To create an invoice, follow the steps below:

1. Click Invoices from the menu, then select Create invoice.
2. Choose an existing customer, or create a new one by entering their name, address, and email address.
3. Decide when you want to be paid and set the date in the Due Date field.
4. Tap Add product & service to add items or services you sold. Enter a description of the service.
5. Hit Flat rate or By hour from the dropdown menu. Or select By item if you're charging for a product. Enter an amount. Then select Add to invoice.
6. To add more items to the invoice, hit Add work.
7. When you're ready, select Send invoice to email your invoice. You can also select the arrow and Preview to see what your customer will receive.

To learn more about adding products and services to an invoice and sending it to your customers, check out this article: Create invoices in QuickBooks Self-Employed. You can also find other helpful articles here for guides and tutorials. 

Moreover, I'll add an article to learn more about how QuickBooks Self-Employed calculates your taxes. Please check out this article for more guided information: Automatically estimate your income tax.

You can enter your response by tapping the reply button if you need assistance or more information regarding your sales taxes. I'm always happy to help. Have a good one!