The Value Added Tax registration threshold has risen to £83,000 from 1 April 2016. If you have made sales of goods or services totalling more than £83,000 over the last twelve months, then you must register for VAT if they are VATable. You are expected to do this every month by looking back at a moving twelve month window. We can help here.
If you expect to make supplies of goods or services totalling more than £83,000 in the next month alone, then you must also register for VAT. This could the consequence of a big order.