I am unable to get Shipping address from Response of CHECKOUT API. Sometime it include customer id but sometime there is no customer id why ?
With the Checkout API the response won’t include the shipping address. If you have ask_for_shipping_address set to true the Square Checkout collects shipping information on your behalf and stores that information with the transaction information in the Square Seller Dashboard.
If you have the customers shipping address you can include the pre_populate_shipping_address in the CreateCheckout request and the buyer’s shipping information is prepopulated on the checkout page as editable text fields.
@Bryan-Square - when I use Zapier to get completed orders to either an external system like sheets or even a woocommerce, the API for completed orders does not include the shipping address (its null). I collect the shipping address during checkout and it is on the transaction. Any suggestion how I can get that shipping address?
Where is the checkout happening. Is it with our online store? Do you have some example orders we can take a look at? 
The process is 1. create an invoice manually in square 2. customer pays invoice and MUST provide shipping address 3. I want to send this invoice information to woocommerce (since customers can order via manual invoice or via web) and easier to print shipping/packing slips if order goes to woocomerce. However, I am unable to send shipping information from that invoice
Since this is with the WooCommerce integration it would need to be something that they add. All functions with that integration is managed by WooCommerce.