Hello, my name is ***** ***** I am a qualified lawyer happy to help you.
If you sell online and it is to the UK customer base then the Consumer Rights Act 2015 will apply - as you sell online they will automatically have a 14 day cooling-off period so this means they can change their mind (for any reason) and expect a refund.
They will also have further rights even after the 14 day period, specifically that the product or service must be "as described", "fit for purpose", and of "reasonable quality" (if this is a product).
You will also need to have a GDPR notice which deals with the customer's data, in other words, to comply with the current data protection law (General Data Protection Regulations). You only need a notice on your website to deal with "GDPR" and there are templates available so that you can ensure your business complies with this.
You should have terms and conditions to trade - they should be fair and not inherently unreasonable. For example, if you said "no returns", or "no refunds", this would be in breach of the cooling-off period which allows UK customers the 14 day cooling-off period.
I can't think of anything else which would be vital here. It would be those two issues so you do not fall foul of UK laws.
I hope this answers your question – if so could you please click 5 stars at the top of your screen, that will give me a rating on the site and I can answer any follow up questions at no extra charge.