"finalize your order" is correct and usable in written English. You can use it when you want to ask someone to complete a purchase. For example, "Please finalize your order so that we can begin processing it.".
Finalize your order for trophies, prizes, and memorabilia based on your final registration date numbers.
After you finalize your order, you'll get your customized polo in about three weeks.
Finalize your order.
The Shopping Cart will be displayed for you to review and finalize your order.
Make a pile of books for each buyback service as you finalize your orders, or put a sticky note with the name of the buying site on each book cover to prevent accidentally promising the same book for sale multiple times.
Depending on where you buy your carpet, the retailer may send an installer out to recheck the measurements before finalizing your order.
If everything looks good, you're ready to begin entering information about yourself, such as your name and billing information, and finalizing your order.
Being a terminologist, I care about word choice. Ludwig simply helps me pick the best words for any translation. Five stars!
Maria Pia Montoro
Terminologist and Q/A Analyst @ Translation Centre for the Bodies of the European Union