## Billable hours are not 40
Assume 50–70% utilization after admin and hunting work. Target net lifestyle from Net salary thinking, then gross-up with Self-employment tax and downtime. Freelance developer day-rate calculator and Contractor day rate are starting points, not gospel.
## Runway before the big client
Cash runway months tells you how long you can say no to a bad rate. Invoice with Invoice with tax and written scope. Scope creep is an unpaid second job.
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Note: Educational content from Calcly United Kingdom. Official sources (HMRC — PAYE/NI simplified annual model.) and licensed professionals take priority in United Kingdom.