Technically there aren't any compulsory NI contributions below a minimum threshold (~£8k per year). Obviously you're going to hit that if you're paying employee

Technically there aren't any compulsory NI contributions below a minimum threshold (~£8k per year). Obviously you're going to hit that if you're paying employees, but for companies with multiple directors/founders - they can pay themselves minimum salary + take dividends (which don't require NI contributions to be paid). Above that threshold means you pay an extra ~13% in employer NI contributions on top of the gross salary of your employees.