shift-swap

---
name: shift-swap
description: Turns shift swapping from an argument in a group chat into one written rule, a five field swap slip, and a log that proves who was meant to be on and who approved the change. Use when shifts get covered by WhatsApp, nobody is sure who is on Saturday, and somebody did not turn up.
---

# One rule for swaps, and the end of two hundred unread messages on a Sunday

You give me your rota, the group chat where swaps currently happen, and the list of who holds which ticket: personal licence, allergen training, keyholder, first aider. You get back a one page swap rule written in the words your team use, a five field swap slip they can send from a phone in twenty seconds, a running swap log kept in one place, a ninety second check the duty manager runs before approving anything, and a monthly sheet that shows nobody has been quietly pushed over the working time limits by a run of covers nobody counted.

## What it does

1. **Write down what the rota already promises each person, before you write any swap rule.** Pull the written statement you gave each member of staff on their first day. GOV.UK says the statement must include "hours and days of work and if and how they may vary (also if employees or workers will have to work on Sundays, during the 'night period' or take overtime)", and that "The employer must provide the principal statement on the first day of employment". For each person write one line: contracted hours a week, the days they are committed to, whether those days are fixed or variable, and whether they have signed anything about the 48 hour week. If a statement is missing or says nothing about hours, that is the first thing to fix, because a swap rule sitting on top of a contract nobody wrote down is a rule you cannot enforce. Do not guess the missing ones. Write "not recorded" and put a date beside it.

2. **Name the one place a swap becomes real, and say out loud that the group chat is not it.** Pick a single log: a printed sheet by the pass, a shared spreadsheet, a page in the rota app. Every swap lands there or it did not happen. The Information Commissioner's Office, writing about keeping employment records, says you "could store employment records centrally rather than locally, so you are not dependent on the availability of individual managers for access". A swap that lives only in a manager's phone dies when that manager is off, when they change phone, or when they leave. The group chat can carry on, and probably will, but the rule is one sentence: a message is a request, the log is the answer. Print that sentence and put it where the rota is.

3. **Cut the swap slip down to five fields so it can be sent while somebody is walking to the bus.** Date of the shift. Shift start and finish. Who is giving it up. Who is taking it. Who approved it, and at what time. Nothing else. No reason, no apology, no medical detail, no family circumstances. The Information Commissioner's Office says you "must identify the minimum amount of personal information you need to hold about your workers, and not hold more information than that", and a swap log that fills up with "my mum is in hospital" is a record you now have to protect, justify and delete on a schedule. If somebody volunteers a reason, it does not go in the log.

4. **Give the duty manager four checks and ninety seconds, in this order.** First, the ticket check: can the person taking the shift legally and safely do it, which means personal licence if they are the only one on for alcohol, allergen training if they will be taking food orders, keyholder if it is a close. Second, the rest gap: GOV.UK states "Workers have the right to 11 hours rest between working days", so a close finishing at 00:30 cannot be followed by an open at 09:00. Third, the break: "Workers have the right to one uninterrupted 20 minute rest break during their working day, if they work more than 6 hours a day", so if the swap turns a five hour shift into a nine hour double, the break has to appear on the rota, not be assumed. Fourth, the weekly rest: the right is to "an uninterrupted 24 hours without any work each week" or "an uninterrupted 48 hours without any work each fortnight", which a person picking up four covers in a row quietly loses. Any check fails, the swap is refused and the reason is one word in the log: rest, ticket, break, or cover.

5. **Count the 48 hour average once a month, not once a swap.** Regulation 4(1) of the Working Time Regulations 1998 says "a worker's working time, including overtime, in any reference period which is applicable in his case shall not exceed an average of 48 hours for each seven days", normally averaged over 17 weeks. Regulation 4(2) puts the duty on you, not on the person who took the extra shifts: "An employer shall take all reasonable steps, in keeping with the need to protect the health and safety of workers, to ensure that the limit specified in paragraph (1) is complied with in the case of each worker employed by him in relation to whom it applies." So once a month, total each person's rostered hours including every swap they picked up, divide by the weeks, and list anyone over 45. Anyone under 18 is a hard stop, not an average: GOV.UK says "If you're under 18, you cannot work more than 8 hours a day or 40 hours a week", and a sixteen year old kitchen porter covering a Saturday double is the most common way a small kitchen breaks this without noticing.

6. **Treat the opt-out as a separate piece of paper, and never as something a swap implies.** GOV.UK says an opt-out from the 48 hour week "must be voluntary and in writing", that "Your employer cannot force you to cancel your opt-out agreement", and that a worker cancelling one "must give your employer at least 7 days' notice" and "may have to give your employer up to 3 months' notice depending on what's in your agreement". Somebody agreeing to cover Friday is not agreeing to opt out. List who has signed one, with the date. Anyone not on that list gets their swaps refused at 48, not argued with at 52.

7. **Do the night check separately, because nights are where hospitality rotas break the rules quietly.** GOV.UK says "Staff who regularly work at least 3 hours during the 'night period' are night workers", that "The night period is 11pm to 6am, unless the worker and employer agree a different night period", and that "Night workers must not work more than an average of 8 hours in a 24-hour period", usually averaged over 17 weeks. A late bar close plus a clean down is three hours after 23:00 without anyone calling it night work. Mark on the rota which shifts cross 23:00, count who is doing three or more hours of that regularly, and put them on the monthly sheet with their own average.

8. **Set a cutoff, and say who owns the shift when the swap fails.** Pick a time: swaps requested more than 48 hours before the shift go in the log and are approved or refused within twelve hours; inside 48 hours they are a phone call to the duty manager, not a message. Then write the sentence that stops every argument: until a swap is approved in the log, the shift belongs to the person originally rostered. That is the whole point of the rule. Nobody gets to post "anyone cover Saturday?", get no reply, and treat silence as cover. Add what happens if a swap turns into a no show, and make it the same procedure you would use for any other absence, handled by your usual process rather than invented on the night.

9. **Review the log monthly, then take out what you no longer need.** Once a month look for three patterns: the same person giving shifts away every week, which is usually a rota that does not fit their life; the same person picking everything up, which is the one heading for the 48 hour list; and the same shift nobody wants, which is a staffing problem wearing a swap costume. Acas warns that a change to a contract can happen through custom and practice, where "terms and conditions change over time and everyone's agreement can be implied", so if you have let one person move permanently onto Tuesdays by swapping every week for a year, write that down properly rather than leaving it informal. Then prune: the Information Commissioner's Office says that once you no longer need workers' information "you should erase it or, if possible, anonymise it". Keep the swap log as long as you keep your rotas and pay records, ask your accountant or HR adviser what that period is, and delete the WhatsApp thread contents you copied out.

## Then it checks

1. Every person on the rota has a line recording contracted hours, committed days, whether hours vary, and whether an opt-out is signed, or the words "not recorded" with a date.
2. Every swap in the log has all five fields filled, including who approved it and the time, and no swap sits in the log approved by nobody.
3. No approved swap leaves less than 11 hours between the end of one shift and the start of the next for either person involved, and any shift over six hours shows a 20 minute break on the rota.
4. The monthly sheet lists every person's average weekly hours including swaps, names anyone over 45, and shows anyone over 48 as either holding a signed opt-out or having the swap reversed.
5. Nobody under 18 appears on the rota for more than 8 hours in a day or 40 hours in a week after swaps are applied.
6. The swap log contains no reason, no health detail and no family circumstance, and every entry that had one has had it removed with the date of removal noted.

Any check fails: name it, redo that step once. Failed twice: say what is wrong and stop.

## Rules
- Public information only.
- Never invent a fact, a number or a quote.
- Anything sent in someone's name says whose name it is.
- Never write a swap into the log as approved unless a named person approved it, because the value of the log is that it answers one question on a Monday morning: who said this was fine. A log with unattributed entries is a group chat with better formatting.
- Never record why somebody wanted the shift off. A reason in a rota log is health, family or religious information sitting in a file that half the team can see, and once it is written down you have to justify holding it, secure it, and delete it.
- Never treat a run of accepted swaps as a permanent change to somebody's hours. Either it is a swap, in which case it ends, or it is a new pattern, in which case it is agreed and written down. Acas says a change must be agreed by both sides unless the contract allows otherwise.
- This output is a working document prepared for the owner's HR adviser, solicitor or accountant to check before it is used. It does not decide anyone's contractual hours, it is not a working time compliance audit, and it is not employment law advice.

## Built from
- GOV.UK, "Maximum weekly working hours", https://www.gov.uk/maximum-weekly-working-hours and https://www.gov.uk/maximum-weekly-working-hours/weekly-maximum-working-hours-and-opting-out, no publication date shown on the page, read 14 September 2026: the 48 hour average over 17 weeks, the under 18 limits that shaped the hard stop in step 5, and the opt-out wording that became step 6.
- legislation.gov.uk, "The Working Time Regulations 1998, regulation 4", https://www.legislation.gov.uk/uksi/1998/1833/regulation/4/made, no publication date shown on the page, read 14 September 2026: the exact wording of the limit and, more importantly, regulation 4(2) placing the duty on the employer, which is why step 5 is a monthly count the owner runs rather than something left to the person picking up covers.
- GOV.UK, "Rest breaks at work", https://www.gov.uk/rest-breaks-work, no publication date shown on the page, read 14 September 2026: the 11 hours between working days, the 20 minute break above six hours, and the 24 hours a week or 48 hours a fortnight, which are the second, third and fourth of the duty manager's four checks in step 4.
- GOV.UK, "Night working hours", https://www.gov.uk/night-working-hours, no publication date shown on the page, read 14 September 2026: the definition of a night worker, the 11pm to 6am night period and the average of 8 hours in 24, which shaped the separate night check in step 7.
- GOV.UK, "Employment contracts and conditions: Written statement of employment particulars", https://www.gov.uk/employment-contracts-and-conditions/written-statement-of-employment-particulars, no publication date shown on the page, read 14 September 2026: the requirement to state hours and days of work and if and how they may vary, which is why step 1 starts with the written statement rather than with the rota.
- Acas, "Changing an employment contract: Employer responsibilities", https://www.acas.org.uk/changing-an-employment-contract/employer-responsibilities, last updated 10 August 2026, read 14 September 2026: that changes must be agreed by both sides, and the custom and practice warning that shaped the monthly review in step 9 and the third rule above.
- Information Commissioner's Office, "Employment practices and data protection: keeping employment records - Collecting and keeping employment records", https://ico.org.uk/for-organisations/uk-gdpr-guidance-and-resources/employment/employment-practices-and-data-protection-keeping-employment-records/collecting-and-keeping-employment-records/, no publication date shown on the page, read 14 September 2026: central rather than local records, holding the minimum information needed, and erasing what you no longer need, which shaped steps 2, 3 and 9 and the rule about never recording a reason.

# shift-swap

## You are given
A folder from one UK hospitality business holding: the rota for the period, as a spreadsheet, an app export or a photograph of the printed sheet; an export or copy-out of the group chat where swaps currently happen; the written statement of employment particulars for each person, or whatever the owner has instead; the list of who holds which ticket, meaning personal licence, allergen training, keyholder and first aider, with dates; the list of who has signed a 48 hour opt-out, with dates; and each person's date of birth or a marker saying who is under 18. Names are spelled several ways between the rota and the chat, and many swaps exist only as messages.

## Produce
Write into an `output/` folder next to the inputs:

1. `contracted-hours.csv` with these columns in this order: `name`, `contracted_hours_per_week`, `committed_days`, `hours_vary`, `sunday_night_or_overtime_stated`, `opt_out_signed`, `opt_out_date`, `under_18`, `statement_source_file`, `date_checked`. Any value with no source reads `not recorded` and carries the date it was checked.
2. `swap-log.csv` with columns: `swap_ref`, `shift_date`, `shift_start`, `shift_finish`, `given_up_by`, `taken_by`, `requested_at`, `approved_by`, `approved_at`, `outcome`, `refusal_reason`. `swap_ref` is S001 upward. `outcome` is exactly one of `approved`, `refused`, `not approved by anyone`. `refusal_reason` is exactly one of `rest`, `ticket`, `break`, `cover`, or empty where the outcome is approved.
3. `swap-checks.csv` with columns: `swap_ref`, `person`, `previous_shift_finish`, `next_shift_start`, `hours_between`, `rest_11_hours_met`, `shift_length_hours`, `break_20_minutes_on_rota`, `consecutive_days_worked`, `longest_gap_without_24_hours_off`, `ticket_required`, `ticket_held`, `ticket_expiry`, `check_result`. One row per person affected by each swap, so a swap produces two rows. `check_result` is `all four met` or names the first check that is not met.
4. `monthly-hours.csv` with columns: `name`, `reference_period_start`, `reference_period_end`, `weeks_in_period`, `rostered_hours`, `swap_hours_added`, `swap_hours_given_away`, `total_hours`, `average_weekly_hours`, `over_45`, `over_48`, `opt_out_signed`, `under_18`, `longest_day_hours`, `highest_week_hours`. Sorted by average weekly hours, highest first.
5. `night-workers.csv` with columns: `name`, `shifts_crossing_2300`, `hours_after_2300_total`, `average_hours_after_2300_per_shift`, `three_or_more_hours_regularly`, `average_hours_per_24_hour_period`, `reference_period_start`, `reference_period_end`, `source_file`.
6. `tickets.csv` with columns: `name`, `personal_licence`, `personal_licence_expiry`, `allergen_training_date`, `keyholder`, `first_aider`, `source_file`, `date_checked`.
7. `swap-slip.txt` - the blank five field slip, with exactly these five fields and nothing else: date of the shift; shift start and finish; who is giving it up; who is taking it; who approved it and at what time.
8. `reasons-removed.csv` with columns: `swap_ref`, `field_it_was_in`, `type_of_detail`, `date_removed`. `type_of_detail` is exactly one of `health`, `family`, `religious observance`, `other personal`. The detail itself is never copied into this file or any other.
9. `gaps.md` - a numbered list of: every swap with no named approver or no approval time; every person with no written statement on file; every swap failing one of the four checks; every person over 45 average weekly hours; every person over 48 without a signed opt-out; every person under 18 rostered over 8 hours in a day or 40 in a week after swaps; every expired ticket; and every name that appeared in more than one spelling.

## Rules
- Codex records only what is in the supplied inputs, attributed and dated. Never invent a shift, a name, an approval, an hours figure or a ticket.
- Never write a swap into the log as approved unless a named person and a time were supplied. With no approver the outcome reads `not approved by anyone` and the shift stays with the person originally rostered.
- Never copy a reason, a health detail, a family circumstance or a religious observance out of the group chat into any output file. Drop it, count it in `reasons-removed.csv` by type only, and never restate the detail.
- Never state or imply that a rota, a swap or an hours figure is lawful, compliant, safe or acceptable. Show the arithmetic against the limits the owner supplied and stop.
- Never treat a run of accepted swaps as a change to anyone's contracted hours. Record the swaps and list the pattern in `gaps.md`.
- Never average an under 18's hours. The under 18 columns are daily and weekly figures compared against the daily and weekly limits supplied, and an exceedance is a row in `gaps.md`.
- Every date, hour and ticket must trace to a supplied input file named in the row. Never fill a contracted hours figure from the rota when the written statement is missing.
- Use British English, £ where money appears and DD Month YYYY dates. No em dashes.
- Every file ends with this line: this is a working document prepared for the owner's HR adviser, solicitor or accountant to check before it is used. It is not advice, it does not decide anyone's contractual hours, and it is not a working time compliance audit.

## Return
The absolute path of each file written, the row count of each CSV, the number of swaps read from the chat and how many had a named approver, the number failing each of the four checks broken down by reason, every person over 45 average weekly hours with their figure, every person over 48 and whether an opt-out is on file, every person under 18 exceeding a daily or weekly figure, the count of night workers identified, the number of personal details removed by type, and the `gaps.md` item count.