Reorder points, purchase orders and pick lists for a shop that has outgrown the spreadsheet
When the stock spreadsheet stops working: how to set a reorder point with the sums, what a purchase order and a bin-sorted pick list buy you, cycle counts, when a 3PL makes sense, and which of it each Orbit plan includes. Checked 9 November 2026.
This guide is for a shop doing 30 to 300 orders a day, where the stock spreadsheet has started to say things the shelf does not. It covers when stock control needs to become a system, the reorder point maths, purchase orders, bins and pick lists, cycle counts, fulfilment houses, and which of these each Orbit plan includes. Disclosure: we build Orbit Commerce, a UK ecommerce platform, so weigh the Orbit parts accordingly. Every outside fact was read at its source on 9 November 2026.
In short
- A reorder point is the sales you expect while a delivery is on its way, plus a safety margin. Buy when stock plus what is on order falls to it.
- A purchase order is the record of what you asked for, at what price, due when. Receive against it and the stock history explains itself.
- Bins and one bin-sorted pick list turn a zig-zag per order into one pass down the aisles.
- Count a slice of stock every week, not everything once a year. Your accountant still needs a year-end value.
- On Orbit, stock by location, transfers, the history and the Low stock filter come with every plan; reorder points, purchase orders, bins, pick lists, cycle counts and the batch workbench come with the Enterprise plan.
When does stock control need to become a system?
A spreadsheet is a fine stock system for one person and a hundred lines. It stops being one at a predictable point:
- You have sold something you did not have, twice in a month.
- Nobody knows what is on order, so a line is reordered while it is on a pallet.
- Reordering means walking the shelves on a Friday and typing an email.
- The stocktake takes a weekend and finds differences nobody can explain.
- A customer asks when it will be back and the answer is a guess.
At 30 orders a day with three lines each you make about 90 picks; at 300 it is close to a thousand. Somewhere between, the question changes from “how many have we got” to “when does it run out, what is on order, and where is it on the shelf”. The operating model underneath is in our post on inventory and fulfilment without the chaos; this one is the layer above.
How do you work out a reorder point?
A reorder point is the stock level at which you buy. Three parts:
- Sales per day. Units sold over the last four weeks, divided by the days the line was in stock (28 if it never ran out), so a sell-out does not drag the rate down.
- Lead time. Days from order to shelf, from the supplier’s last few deliveries, not their website. Note the longest one too.
- Safety stock. The margin for a busy week or a late delivery: busy-week daily sales multiplied by the longest recent lead time, minus your normal lead-time demand.
Then reorder point = (sales per day × lead time) + safety stock. When stock plus what is on order falls to that figure, you buy. One line, with our own example figures:
| Figure | Example | How you get it |
|---|---|---|
| Sales per day | 12 bags | 336 sold in the last 28 days, divided by 28 |
| Lead time | 10 days, 14 at worst | The supplier’s last six deliveries |
| Lead-time demand | 120 bags | 12 a day for 10 days |
| Safety stock | 90 bags | A busy week at 15 a day for the worst 14 days is 210; take off the 120 |
| Reorder point | 210 bags | 120 plus 90 |
| Order quantity | 168 bags, rounded to the case | Two weeks of sales if you order fortnightly |
Compare it with stock plus incoming, not stock alone, or you order a line twice while the first delivery is in transit.
How much should you order each time?
The textbook answer is the economic order quantity, which balances the cost of placing an order against the cost of holding stock. You need the lesson, not the formula: carriage, your time and supplier minimums push you towards fewer, bigger orders; cash tied up, shelf space and lines going stale push you towards smaller, more frequent ones. So cheap, slow lines are bought months at a time, expensive or perishable lines little and often, and the case size settles the number.
ABC analysis: which lines deserve the maths
You do not need reorder points on 2,000 lines. Sort the catalogue by revenue: the A lines bring in the first 80% of it and are often a small share of the range, B lines the next 15%, C lines the rest. Set reorder points on the As and Bs, check the As weekly, and let the Cs run on a low-stock flag. Re-grade before your busy season.
What should a purchase order carry?
A purchase order is the record of what you asked for; the delivery, the invoice and the argument about the short case all refer back to it. Email it as a PDF and give it a number the supplier will quote back. It carries your PO number, the date and the expected delivery date; the supplier, your account number and the contact; one line per item with their SKU and yours, quantity, unit cost and currency; carriage and other charges; and your payment terms, delivery address and notes. With a buyer on the team, add an approval step above a value you choose.
Receiving against it. Count the delivery against the order, not the delivery note. Record what arrived, reject damaged units with a note, and expect a 200-unit order to land as 120 and 80 a week apart. Stock goes up by what came, the order shows what is still owed, and the history reads “received against PO-1041” instead of “plus 120, Tuesday”.
Landed cost. Spread the carriage, any duty and other charges across the units and you have what the stock really cost, the figure your margin should be worked out on: £4 a unit with £120 of carriage on 200 units lands at £4.60. If the supplier bills in euros or dollars, record the order in their currency.
These records are for the suppliers whose goods you buy and hold in stock; where a wholesaler feeds your catalogue and ships for you, the data flows the other way, as our post on getting suppliers’ catalogues onto your website explains.
Backorders: selling what is on its way
Sell a line at zero only when a purchase order is in transit and you can give the customer a date. Allow it per product, never store-wide, put the date on the product page and in the order email, and ship the moment goods-in covers the order.
Why do bins and pick lists matter at 100 orders a day?
A pick list is the warehouse’s document: every unit still to pick across a run of orders. A packing slip is the customer’s: one order and what is in the box. At a few orders a day the slips do the picking job. Past that, two habits change the morning.
Give every item a bin and pick a batch from one sorted list. A bin is a shelf label, A-12, not a stock count. Picking order by order means aisle A, then aisle D, then back to A. Twenty orders from one list sorted by bin means one pass, A-2 then A-10 then A-12, each line showing the total units for all twenty, sorted into orders at the pack bench. Walking is most of a picker’s day.
Verify at the pack bench. Scan each unit’s barcode against the order before it goes in the box; the wrong colour and the wrong size are the returns a scan catches for nothing. A picker needs orders, stock and the lists, not prices or refunds; give them a role that matches.
Should you still do an annual stocktake?
Not as your control. An annual count finds a difference months after the cause, so the figure gets corrected and the cause never fixed. A cycle count does the same job a slice at a time: this week bins A-1 to A-20, next week one category, a whole location after a busy month. Review each variance, then apply the lot so the history records the adjustment with a reason. Count A lines most often.
The year-end value is a separate matter. For the self-employed, gov.uk lists “the value of stock and work in progress at the end of your accounting period” among the records a business using traditional accounting must keep (gov.uk, business records if you are self-employed, read 9 November 2026). HMRC’s Business Income Manual gives “the lower of cost or net realisable value” as a basis for valuing stock (BIM33115, updated 4 August 2026, read 9 November 2026). Companies follow their accounting standard. Rolling counts give an accurate quantity on any date; your accountant says which date and figure they want.
When should you move to a 3PL instead?
A fulfilment house (a 3PL) stores your stock, picks and packs your orders and buys the postage, for a fee per order and a fee per shelf or pallet. It is the right move when the constraint is physical: no space, nobody to staff the afternoon cut-off, or orders that should ship from somewhere your team is not. It is the wrong move for a problem the spreadsheet caused.
Most fulfilment houses quote per brand. Fulfillable, a UK one, publishes storage per location per day (a pick bin at £0.05, a shelf at £0.15, a pallet at £0.80), calls its pick and pack fee negotiable as volume rises, and states a minimum monthly invoice charge of £1,000, prices excluding VAT where applicable (fulfillable.co.uk, read 9 November 2026). Do your own sum first: your picker’s hours, space and packaging divided by orders a month, against the per-order fee plus storage and the minimum. If you move, keep the stock record, the purchase orders and the customer promise in your own system.
Where Orbit fits
Orbit runs stock control on every plan and the warehouse operations on the Enterprise plan.
| Job | Solo, Team and Pro | Enterprise |
|---|---|---|
| Stock by location, transfers, history | Yes: no cap on locations, on hand, committed and available side by side, every change logged by name | The same |
| When to reorder | The Low stock filter at 10 or fewer available, your own sheet, Nebula’s restock suggestion | Reorder points and safety stock per item and location, run-out dates, ABC grades, a morning digest |
| Purchase orders | Your own PDF; receive by adjusting stock with the reason Received | Suppliers with lead times, approval, PDF emailed with your terms, receiving by barcode or SKU, landed cost |
| Picking and packing | Packing slips printed in bulk from the Orders list | Bins, one bin-sorted pick list per run, batches of up to 250 orders, scan to verify |
| Counting | Count, then Set the figure with the reason Count, or import a count by CSV | Cycle counts by bin, category or location, variances applied in one go |
| Backorders | Allow backorders per product; stock goes below zero to show what you owe | The same, and orders wait in Awaiting stock until goods arrive |
On Solo, Team and Pro, from £25 a month, inventory management is the middle column (walk-through: our stock control guide). Run the reorder maths in a sheet for your A and B lines against the Low stock filter. Ask the Nebula assistant (every plan, with a monthly allowance) what needs reordering from your sales, for any report by name with its CSV, or to adjust stock across every location in one instruction. Let the Import/Export plugin fetch a supplier’s or warehouse’s stock file from a URL, FTP or SFTP on a schedule.
On Enterprise, the warehouse operations are the right-hand column, built in. They give you a suggested reorder point for an item kept in one location (its preferred supplier’s lead time multiplied by daily sales, plus your safety stock), and run-out dates from the last 28 days of sales across the shop with out-of-stock days left out. You also get ABC grades once the shop has 30 orders in 28 days and a morning reorder digest if you opt in. Create purchase order fills in a quantity to cover the lead time plus two weeks of sales, less what you hold and what is on its way. Units on open purchase orders count as incoming until 30 days past their expected date, and received stock is valued at weighted average cost.
Enterprise is £999 a month, or £749 a month billed yearly, ex VAT, and also carries B2B company accounts and price lists (see our trade counter post) and a dedicated account manager (the Enterprise plan). If you kept your Stocky exports, the import wizard brings them in; see our Stocky migration guide. The 14-day trial can start on Enterprise, so you can run a fortnight of real purchasing before you decide.
Read next: fifteen shop jobs you can stop doing by hand, getting your wholesale range into UK online shops and hiring your first shop assistant.
Questions people ask about reorder points, purchase orders and pick lists
What is a reorder point?
The stock level at which you raise a new order: the sales you expect while the delivery is on its way (daily sales multiplied by the supplier’s lead time) plus a safety margin for a busy week or a late delivery. When what you hold plus what is on order falls to that level, you buy.
How much safety stock should a small shop hold?
Enough to cover the gap between a normal spell and a bad one. Multiply your busy-week daily sales by your supplier’s longest recent lead time, then subtract your normal lead-time demand. A line selling 12 a day with a 10-day lead time, a busy week of 15 a day and a worst lead time of 14 days gives 210 minus 120, so 90 units.
What is the difference between a pick list and a packing slip?
A pick list is for your warehouse: every unit still to pick across a run of orders, sorted by bin so the picker walks the aisles once. A packing slip is for one order and goes in the parcel. At a few orders a day the slips can double as pick lists; past that, a sorted list is quicker and makes fewer mistakes.
Do I still need an annual stocktake if I do cycle counts?
Not as a control, if every bin is counted on a rolling cycle and variances are applied as you go. You still need a stock value at your year end: gov.uk lists the value of stock and work in progress at the end of the accounting period among the records the self-employed keep, and HMRC’s manual accepts the lower of cost or net realisable value as a valuation basis. Ask your accountant which date and figure they want.
Which Orbit plan includes reorder points, purchase orders and pick lists?
Enterprise. Every plan has stock per location, transfers, the movement history, the Low stock filter at 10 or fewer available, backorders per product and CSV import and export. Reorder points and safety stock, run-out dates, ABC grades, purchase orders and receiving, bins, pick lists, cycle counts and the batch workbench are part of the Enterprise plan; on Solo, Team and Pro the Low stock filter, the stock history and the Nebula assistant do the reordering job.
Start this week with the maths on your twenty best lines. When you want the system to do the arithmetic, the 14-day free trial, no card required, can start on Enterprise with every warehouse tool switched on.