Hello again Desiree 869,
These are great questions and I'm happy to go over these options with you so you're accurately recording payments and sales tax in your books.
When it comes to recording payments, it's typically best to record them with the date the payment was received outside of the program. This helps ensure that your monthly reconciliations are accurate since those are compared directly against your bank statements. When you go to reconcile for January, you're going to want to see the relating transaction in your reconcile screen of QuickBooks Desktop. Learn about reconciliation here: Reconcile an account in QuickBooks Desktop
To change the dates entered on a transaction, it's as simple as opening the transaction again and editing the date. You can do this in many ways, but one of the easiest is to go to the Customers menu, click Customer Centre, then single-click to select the customer in question. There, you'll see a list of transactions. Double-click the one you need to open it for editing.
As for sales tax, QuickBooks Desktop gives you the option to File Online or file outside of the program with the Paper or other filing method. If you have a return with a $0 balance, an amount owing, or a refund of $10,000 or less, you can use the File Online option. A 4-digit access code is printed on the working copy of your personalized return.
I recommend going through the sales tax articles in community to learn more. The collection starts with Set up sales tax in QuickBooks Desktop and there are hyperlinks to other related articles on it.
For further questions and assistance, I recommend getting in touch with QuickBooks Desktop support to give the specifics of your situation and learn all the options. Learn more here: Intuit QuickBooks Desktop software support policies
Enjoy your week!