In general, we recommend double-checking all the details and files before processing to check out. If, however, you found a mistake in the file or address, or need to cancel the order due to other reasons, it is possible only if the order hasn't been sent to printing. If the status of the order is other than "New" (either "Printed" or "Shipped"), it's not possible to change or cancel the order, it will be printed anyway.
Usually, we send all files to production at midnight in the region of production, thus, there is a higher probability to cancel the order on the same day it was placed. However, during the peak season, which is from October to December, we start uploading print jobs 2 times a day, thus, it might not be possible to cancel the order on the same day.
You can cancel orders using our dedicated APIs or through the API Portal.
Read more on order flow and status here.