In the UK? Pop your sample in the prepaid envelope (no need to get a stamp) and post it back on the same day it was taken, using any Royal Mail post box in the UK.
If you’re in Ireland, you’ll need to return your sample to us using a post office on the same day you took your sample. This is so you can get your tracking details.
Testing on a weekend? Saturdays should have postal collections, so collect a sample and post as planned, just be sure to post it before the last collection time! If your testing day falls on a Sunday, collect a sample as planned then keep the sample at room temperature (this stops your sample from ageing) and post it first thing on Monday. Please check the postal website for more information on your local services. If you are posting from Ireland, please check your postal service operation dates before sending as postal services may be paused over the weekend.