The session rate is not the cost
Where an engagement falls inside the off-payroll working rules, the practice carries employer National Insurance on top of the rate — 15% above a £5,000 secondary threshold. That total, not the headline session rate, is the figure to compare against the cost of a salaried appointment.
And the duty to determine is yours
A GP practice with a registered patient list is a public authority for the purposes of Chapter 10, and there is no small-client exemption for a public authority. Practice size is irrelevant: a two-partner practice must determine the status of a locum engaged through a personal service company and issue a Status Determination Statement, exactly as a large one must. That has been the position since 6 April 2017.
Getting it right in both directions matters. Treating a genuinely self-employed locum as inside the rules costs the practice money it did not need to spend.
What a Status Determination Statement has to do
It is not a box to tick. The practice reaches a conclusion on status, states it, gives the reasons for it, and passes it to the worker and to the party it contracts with. Reasonable care has to have been taken in reaching it — a blanket determination applied across every locum without looking at the individual engagement is the thing HMRC challenges most readily. If the worker disagrees, the practice has to respond within 45 days.
The factors are the ordinary ones: control over how and when the work is done, a genuine right of substitution, who carries financial risk, and mutuality of obligation beyond the individual booking. HMRC's CEST tool is the starting point, and the output is only as good as the answers — which is why keeping the working, not just the conclusion, is what makes a determination defensible two years later.
The other cost nobody puts in the comparison
Pension. A locum who elects to pension their work does so on forms A and B, and a GP doing self-employed ad hoc work uses the GP Solo form monthly — which is a real administrative load on the practice rather than on the locum. A salaried appointment carries employer contributions instead, at a rate that is not optional.
And there is a superannuation point that catches practices on the way out rather than the way in: where a GP provider, non-GP provider or salaried GP has underpaid contributions for a year, the arrears are paid by the surgery, not the individual — even if they have left. Overpayments are reimbursed to the surgery too. A departing partner's shortfall lands on the continuing partners unless the deed says otherwise, which makes the partnership deed and the leaver mechanism the operative documents rather than the pension forms.