I can't see the Jan21 IAS on the GST page do I have to complete the Dec 20 BAS before it shows?

Welcome to the Community, @cam-mclay.

Yes, you have to complete or lodge the Dec-2020 BAS first. After that, the GST centre will show the Prepare IAS for Jan-2021.

Here's how to do it:

1. In QuickBooks Online (QBO), go to the GST tab and select Prepare BAS.
2. Finalise your GST obligations by reviewing the total sales (including GST), total purchases, GST collected on sales, and GST paid on purchases.
3. Click on Next then add or review the Income Tax instalment amount.
4. If the instalment amount needs to be updated, tick I need to adjust the instalment amount and adjust it accordingly.
5. Press Next again then hit Mark as lodged to close the tax period in QuickBooks.

For more insight about preparing your BAS or IAS in QBO, consider checking out this article: Lodging BAS and IAS.

Feel free to post a comment below if you have any other questions. I'll be more than happy to answer them. Have a great day!