How do I change the sales tax percentage It went down to 6.625% in New Jersey

Thank you for adding a reply and sharing you thoughts, @Anonymous.

Yes, we can change the sales tax rate by going to the item list and locate the sales tax item we wanted to edit. However, we also have the option to deactivate the old sales tax item with the old rate and create a new one.

Both deactivating and editing the sales tax rate won't affect the previous transactions/invoices created using the old rate. For the detailed process on how to edit the sales tax rate, refer to the steps given above. On the other hand, to inactivate the old sales tax item and rate:

1. Go to Lists.
2. Select Item Lists.
3. Locate the Sales Tax Item.
4. Check the box beside Item is inactive to inactivate the item.
5. Click OK to save the changes.

For additional reference about sales tax set up in QuickBooks Desktop, you  may check this: Set up sales tax in QuickBooks Desktop.

Our doors are always open here in the Community page. Feel free to click the Reply button if you have any other sales tax questions. Have a good day!

Can the sales tax rate be changed before the effective date? Is there a field to enter the effective date? 

Welcome to the thread, @Tamac.

You can change the sales tax rate whenever you'd want. Since when creating a transaction and apply the sales tax, that would be the effective date. 

Moreover, you can add a Memo to the transaction to manually track the effective date of the Sales tax.

To edit the sales tax rate, follow the below steps:

1. Go to List menu at the top, then pick Item list on the drop-down.
2. Locate your Sales Tax item, then right-click and select Edit item.
3. Enter the new rate on the Tax Rate (%) section, then hit OK.

For future reference, you can also check out this article and click the Sales tax item drop-down on step 4 for more information: Set up sales tax in QuickBooks Desktop.

I'd be glad to answer should you have any additional questions about the process, just leave a comment below. Have a wonderful day ahead and take care.