The Second Invoice: What Seasonal Cover Costs After the December Wage Run

Every December, the same arithmetic appears on a manager's desk: four people, four weeks, an hourly rate, and a total that looks survivable against peak trading. It is the wrong total. The wage run is only the first instalment of a seasonal hire, and the second one arrives when the tills have stopped ringing, the decorations are down and nobody is watching the payroll account.

For an owner-manager, the useful discipline is to price seasonal cover as a complete package at the point of agreement, not to discover the remainder in the January bank statement. The statutory figures below are illustrative and should be checked against the rates in force when you are hiring, but the shape of the calculation does not change.

Why the December figure understates the bill

An hourly rate covers hours worked. It does not cover hours not worked but still paid, contributions owed on the wages, or the paperwork that must exist before the first shift begins. Seasonal cover is short in duration but it is not a simplified form of employment: the same obligations attach from day one, and several of them crystallise only when the engagement ends.

That timing mismatch is the trap. The peak period generates the revenue; the compliance costs settle in the quiet weeks that follow, when there is less cash coming in to absorb them.

Four costs that settle after the peak

Accrued holiday. Statutory holiday entitlement is 5.6 weeks a year for a full-time worker, pro rata for anyone on a short contract. For staff on irregular hours, the established method is to accrue 12.07% of hours worked, since the 5.6 weeks represent 12.07% of a 46.4-week working year. That accrual is a real liability even if no leave is taken during the engagement; on termination it is normally paid out. A temp who works 150 hours in December carries roughly 18 hours of accrued holiday behind them.

Pension auto-enrolment. Eligible jobholders must be enrolled, and the employer minimum is 3% of qualifying earnings. Postponement of up to three months is permitted, which means many short seasonal engagements never generate a contribution — but the assessment is not optional, and a worker who is engaged again in the new year, or who has other earnings with you, may already be eligible. Treat the pension line as a probability rather than a rounding error.

Employer National Insurance. At the 15% rate introduced in April 2025, applied above the secondary threshold, the employer contribution on a month of seasonal pay is material. The Employment Allowance may absorb it for eligible employers, but the allowance is not available to every business and should not be assumed.

Right-to-work and onboarding administration. Document checks, contracts or written statements of particulars, induction time, uniform, PPE and system access all carry cost. None of it appears on the rota.

A worked model

Take four seasonal staff on £12.50 an hour, each working 150 hours in December — a little under 40 hours a week for four weeks.

The headline rate says £1,875 per person. The full model says roughly £2,425 — an uplift of approaching 30%. That is the number to test against the margin the peak period is expected to generate. If the extra trading does not cover it, the cover is being subsidised by the rest of the year.

The cash-flow calendar matters as much as the total

Costing the package is only half the exercise; the timing determines whether it hurts. Three dates deserve a place in the December diary.

First, the PAYE payment for the December payroll falls due on 22 January if paid electronically. That is a single debit covering income tax, employee NIC and employer NIC, and it lands in the same week as the January VAT quarter for many businesses.

Second, holiday pay on termination falls due with the final payroll, not with the holiday. If seasonal staff finish on 31 December, the accrual is paid then and the PAYE for it is due with the same January payment.

Third, if your accounting year ends on 31 December, any holiday accrued but not yet taken is a liability on the balance sheet. It reduces the profit the year appears to have made, which is correct, but it is better to have planned for it than to explain it.

Before you agree the shift pattern

A short checklist, applied before the rota is signed off, prevents most of the surprises.

• Confirm right-to-work documentation for every direct hire before the first shift, record the date of the check, and repeat it for anyone whose permission is time-limited. For agency staff, confirm in writing that the agency has done so.
• Issue the written statement of particulars where the engagement will, or is likely to, exceed one month. Seasonal contracts that may roll into January should be drafted as such from the outset.
• Decide whether to use pension postponement, and record the decision rather than leaving it to the payroll bureau.
• Check whether repeated seasonal engagements create continuity of employment. Gaps of a week or more usually break continuity, but the pattern of your own hiring is what a tribunal would examine.
• Set the holiday accrual rate in the payroll system at the start, not at the end, so the liability is visible weekly.
• Model the 22 January payment alongside the January VAT and any quarterly rent before committing to headcount.

What to put on the hire sheet

The practical fix is a single seasonal hire sheet that carries the hourly rate, the expected hours, the accrual percentage, the pension assessment outcome, the employer NI estimate and the date of the January PAYE debit. It converts a wage negotiation into a costing decision and gives the person approving the rota something more useful than an hourly rate to compare against the forecast.

Seasonal staff are often the right answer for a business with a genuine December peak. They are rarely as cheap as the rota suggests. Pricing the January tail before the offer is made is not caution for its own sake; it is the difference between a peak that pays for itself and one that is quietly financed by February.