UK Contractor & IR35 Calculators

Most UK contractors are paid through one of three structures: agency PAYE, an umbrella company, or their own limited company. Which one applies depends on your IR35 status, the end client's size, and how comfortable you are running a small business. The take-home difference between these routes on a typical £500 day rate can easily exceed £15,000 a year.

IR35 (the off-payroll working rules) is the rule that decides whether your engagement is genuine self-employment or disguised employment. Inside IR35 income is taxed via PAYE Income Tax and National Insurance with no salary/dividend split. Outside IR35 income flows through your limited company, where corporation tax (19–25%), the £500 dividend allowance and dividend tax rates of 8.75 / 33.75 / 39.35% all come into play.

The calculators below model these flows using current HMRC thresholds: the £12,570 personal allowance, 20 / 40 / 45% Income Tax bands, employee NI at 8% and 2%, employer NI at 15% above £5,000, the apprenticeship levy of 0.5% on umbrella assignments, and the standard salary + dividend mix for director-shareholders. Use them to compare offers, plan drawings, or decide between umbrella and limited company contracting.