Does PAYE allow for correction of accidental errors by the payroll dept?

[WordIsBond]

I would guess if there's a permanent NI difference caused by this, it would be in your favour.

Unless everything from multiple weeks is paid in one week and those other weeks are all paid at zero. Then, you lose the weekly tax-free allowance.

OP mentioned employer NI, the benefit you noted is only on employee NI. Lumping a bunch of pay into one period helps with employee NI but doesn't help with employer NI at all.

[Lambert Simnel]

Quite a substantial benefit indeed.

Paid £1,000 for a week and you pay 89.76 (12% between 160 & 892 then 2% above that.) So £269.28 over 3 weeks.

Get paid £3000 in one week and you only pay £129.76.

The exception is, of course, Directors' NI which is calculated on a cumulative basis in the same fashion as PAYE - precisely because Directors are expected to be able to alter the timing of their payments. Obvs not a consideration when contracting through an umbrella, however.