The core difference
A VAT-registered business adds value-added tax to its sales, can claim back VAT on its own purchases, and files VAT returns. A non-VAT business does not add VAT, but typically pays the simpler percentage tax instead.
Think of VAT as a tax you collect from customers and pass on, while percentage tax is a smaller flat charge on your sales.
The VAT threshold
The deciding factor is usually the VAT threshold, a level of annual gross sales set by law. Businesses whose sales go above it are generally required to register for VAT. Those below it can usually stay non-VAT, though some choose VAT registration on purpose.
Crossing the threshold mid-year can trigger a requirement to register for VAT, so it is worth watching your sales as you grow.
Which is better for you
Neither is automatically better. VAT registration can suit businesses with many VAT-paying suppliers or large clients who prefer VAT invoices. Non-VAT is simpler and often lighter for small operations and the self-employed.
Ask AskOnward how the threshold and the two options apply to your business, or check with a tax professional.