What mailing address should I use on Form 1040 if I spent most of the year in the U.S. (where I had earnings) but moved to Singapore in Nov 2016 (where I had no earnings).

Use the address where you currently reside, so that if the IRS needs to mail you anything, it will get to you.

You can enter either a US or a foreign address in TurboTax.  To enter a foreign address in TurboTax, please follow these steps:

1. Click on the Personal Info tab.
2. In the Mailing address section, click on Edit. 
3. On the screen, Enter your current mailing address, in the Type of mailing address box select Foreign Country.  
4. Enter your information and click Continue when finished.

[Edited | 4/15/2020 | 11:17am PDT]

Thanks for the quick response, TurboTaxIrene. Someone checks our mail daily at our U.S. address, so it sounds like there won't be a problem using our U.S. address. I just wanted to make sure the IRS was okay with that.

As long as they can get ahold of you, the IRS doesn't care!