Understanding Pay Runs

What is a Pay Run?

A payroll describes the chronological progression of an employees payments and deductions. These values are tracked in a "rolling" sequence of statements that we like to call Pay Runs. A pay run represents the calculation of a payslip and the transfer of earnings from the employer to the employee.

Typical chained pay run succession

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Generating a Pay Run

Pay runs are generated entities and not directly created by the user. To generate a pay run, you need to create a pay run instruction job. Once the job is complete, a new Pay Run will be created and added to the object hierarchy along with the resulting calculated pay lines.

Pay Run Rules

Pay runs have a few simple rules to ensure that earnings and deductions are correctly tracked.

  1. The pay run must contain at least one employee

    Pay runs don't make sense without employees to calculate; a run must contain at least one employee to be calculated.

  2. All employees within the run are paid on same date

    A single pay run can only support a single payment date. If employees are paid on different dates within the reporting tax period, a run will be required for each unique date.

  3. The pay run cannot contain calculations for multiple pay frequencies

    All employees within the run must be calculated using the same pay frequency. The pay frequency is stored within the parent pay schedule entity.

  4. The pay run dates must run sequentially

    Pay runs are chained in to chronological sequence. Each subsequent run must follow on from its predecessor without gaps between the end and start dates. The payment date must never be before another payment date within the same pay schedule. If the payment date supersedes a previous calculation, the historic results would be invalidated.

  5. Additional employee pay runs must be marked as "Supplementary"

    In the event that an employee needs another payment within a single reporting tax period, the pay run must be marked as supplementary. More information on supplementary runs can be found detailed below.

Runs, Schedules and Tax Periods.

The pay run represents earnings within a period of time. The duration of this period is defined by the Pay Schedule. Schedules group employees under a single Payment Frequency. The HMRC reporting period (Tax Period) is identified using a combination of Payment Date and Payment Frequency.

Monthly Example:

Pay Schedule: Frequency = Monthly

Pay Run: Payment Date = 2016-10-08

Tax Period: Monthly period 7-2016/17 (2016-10-06 to 2016-11-05)

Weekly Example:

Pay Schedule; Frequency = Weekly

Pay Run; Payment Date = 2016-10-08

Tax Period; Weekly period 27-2016/17 (2016-10-05 to 2016-10-11)

Pay period dates, payment date and tax period.

Pay period dates and tax period dates do not always align

The properties within a pay run include two dates; period start and period end. These dates represent the span of time covered by the pay run, referred to as "the pay period". The duration of the pay period should be equivalent to the pay frequency. Weekly frequency equals a single week, monthly equals a calendar month, four weekly equals four weeks, etc. Pay period dates do not always equal tax period dates. There is no requirement for the employer to match their pay periods to the tax period. The tax period is identified by the frequency of payment and payment date. However, the length (or duration) of the periods (tax and pay) must match.

Monthly Example:

ACME Co runs a monthly payroll for it's employees. The payments are made on the first Monday, one month in arrears.

Pay Frequency: Monthly

Pay Period: 2016-10-01 to 2016-10-31

Pay Day: 2016-11-07 (first Monday)

Tax Period: Monthly period 8-2016/17 (2016-11-06 to 2016-12-05)

Weekly Example:

Example Works Ltd runs a weekly payroll for it's employees. The payments are made on the Friday, one week in arrears.

Pay Frequency: Weekly

Pay Period: 2016-10-03 to 2016-10-09

Pay Day: 2016-10-14 (following Friday)

Tax Period: Weekly period 28-2016/17 (2016-10-12 to 2016-10-18)

Run, re-run and supplementary.

The calculation of an employees payslip is represented by a pay run. In the event that the employee requires a re-calculation of their earnings, it is possible to perform a re-run. If the employee requires an additional payslip within the same tax period, it is possible to create a supplementary run.


Re-runs are a destructive process. During the re-run previous calculation results are deleted and new results are added in their place.

Complete re-run for all employees

In this example the entire run is re-calculated. This process deletes the original run and replaces it with a new run for the payment period. alt text

Partial re-run for a single employee

Partial re-runs allow for re-calculations on a subset of the employees. This causes a new run to be chained to the proceeding run and the original employee calculations to be removed. alt text

Pay Run Rules

To ensure data integrity, re-runs are controlled by a set of rules.

  1. Only the most recent run can be re-run

    It is not possible to re-run a preceeding period. Changes to a preceeding period would invalidate the sequential calculations. Another way to consider this is that you only ever re-run the tail end of the pay run chain.

    For example:

    Pay Run A: Week 1

    Pay Run B: Week 2 (follows from A)

    Pay Run C: Week 3 (follows from B)

    Runs A and B cannot be re-run because they have dependent calculations, only C can be re-run.

  2. Re-runs must match the original run parameters

    The re-run properties must match the values of the run being replaced. Period duration, frequency and payment date must match the original run.

  3. Re-runs must include one or more original employees

    It is not necessary to re-calculate all employees within a run. The re-run can be for one or more of the originally calculated employees.

Supplementary Runs

Some payment models involve an employee receiving multiple payments within a single reporting tax period. Supplementary pay runs are designed to represent this behaviour. If the employee receives multiple payments within the period, then you should use supplementary runs to calculate the additional payments and deductions.

Unlike re-runs, supplementary runs are non-destructive. The extended pay run results are not deleted and are considered when calculating the additional payments. This is important when considering per period limits like tax allowance and National Insurance contributions.

Supplementary Run for single Employee

The following example shows a supplementary run for a single employee. Note that the supplementary run becomes part of the chain and is the predecessor to the following months run.

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Supplementary Run Rules

Supplementary runs follow an additional set of rules to ensure they do not conflict with the existing calculations.

  1. Supplementary runs must extend an existing run

    A supplementary run can only be used to extend pay calculations within a tax period. They cannot reside independently within a tax period.

  2. Supplementary runs must include one or more original employees

    Like re-runs, a supplementary run must include one or more of the paid employees for the supplemented run.

  3. Supplementary payment dates cannot be before other payment dates

    When creating a new supplementary run, the payment date must not be before a preceeding payment date. Setting an earlier date would invalidate the preceeding calculation.

  4. Supplementary period dates must match the extended run

    The period dates of the supplement must match the run that it is extending.