Why your unmetered business water bill changes when your rateable value doesn’t (2026/27)

Here’s an illustrative example. Three bills in a row come to £50, £25 and £37.50. Check the dates on each one. If the charge works out at £1.25 a day, the figures line up exactly.

The daily charge never changed. What changed was the length of each billing period, which happens when bill dates move around, when one period is split across two bills, or when a part-period bill follows a switch or a change of occupier.

If the daily figure is different on each bill, period length isn’t the explanation. Look for a credit or debit for an earlier period, a corrected RV or charge basis, or a change to one of the services being billed. If none of those is shown, ask the retailer to explain the difference in writing.

Either way, you’re entitled to understand the bill. Ofwat’s customer protection code requires bills to show how they were calculated, so it’s reasonable to ask for the annual charge for each service, the daily amount and the exact dates billed. If irregular periods make budgeting hard, ask whether the retailer can bill on a fixed monthly cycle. How a retailer bills is one of the things we compare for you, alongside the retail fee.

England

Without a meter, the wholesaler for your area charges on the property rather than on what comes through the pipe. Most unmeasured business charges are built from two parts for each service, a fixed annual amount plus a charge for every pound of rateable value (RV). Severn Trent’s 2026/27 non-household scheme works this way for water, and again for used water and surface water. Yorkshire Water’s scheme splits its unmeasured sewerage charge into a foul element and a surface water element, both tied to RV.

The RV in question is not the one on your business rates bill. Bristol Water’s 2026/27 wholesale schedule defines it as the figure in the rating valuation list as at 31 March 1990, and uses a Valuation Office Agency assessment for premises that have no such figure. That’s why an English business rates revaluation leaves an unmetered water bill where it was. The rateable value glossary entry explains where those figures came from.

Some sites pay an assessed charge instead. CCW explains that where a meter couldn’t be installed, the charge is usually based on the type of business or the number of employees. Severn Trent and Bristol Water both offer an assessed basis where a meter can’t reasonably be fitted. There’s more in assessed water charges.

Wholesale charges are reset for each charging year from 1 April. Thames Water put the typical 2026/27 change for an unmeasured business bill with both services at 4.1%.

Scotland

Scottish Water’s wholesale charges scheme uses the Live Rateable Value, the most recent valuation set by the Assessor and held on the market’s central systems, and has done so since 1 April 2018. Rateable values are set by the 14 Scottish Assessors, and the latest revaluation took effect on 1 April 2026, based on rental values at 1 April 2025.

A business whose RV went up or down at revaluation will have seen its unmetered water, waste water and property drainage charges move from April 2026, on top of any price change. The Assessor can also revise a value between revaluations when a property changes in a way that affects its rental value. If you think the RV itself is wrong, the challenge goes to the Assessor through saa.gov.uk rather than to your retailer.

The day-by-day basis isn’t a quirk of one retailer. Severn Trent’s scheme says liability for unmetered supplies accrues daily through occupation of the premises. Scottish Water apportions wholesale charges on a calendar day basis. MOSL, the market operator in England, calculates settlement charges daily and takes account of any tariff change on the day it applies.

Ofwat’s customer protection code requires each bill to show your SPID, your tariff and how the bill was calculated. If yours doesn’t make the days or the daily amount clear, that’s a reasonable thing to ask for.

This example is illustrative, with round figures and no real rates. Say a shop’s unmetered water and wastewater charges come to £1,460 a year. That works out at £4 a day.

Now suppose the charges rise by 5% from 1 April, to £1,533 a year or £4.20 a day, and the retailer bills from the 15th of each month. The bill for 15 March to 14 April covers 17 days at £4.00 and 14 days at £4.20, which comes to £126.80. The next one, 15 April to 14 May, is 30 days at £4.20, so £126.

Three bills in a row show three different totals, and the only real change was the April price. Differences like these stay within a few pounds. If your bills are halving or doubling, go back to the day count in the section on big swings above. A correction for an RV that was wrong last year could make one month several times the usual figure while the ongoing charge stays right.

Query it if the daily amount changes at a time other than 1 April and nobody has told you why. The same goes for an RV on the bill that doesn’t match what you’d expect, which in England is the 1990 figure and in Scotland is the Assessor’s current value. Challenge charges for days before you took on the premises or after you left. Severn Trent’s scheme, for example, apportions charges to the day of vacating and starts the next occupier the following day.

Large catch-ups need checking. Ofwat’s code limits how far back a retailer can recover charges once the market has settled that period, and a micro-business must be offered a reasonable repayment plan for a back-bill. Where a wholesaler recalculates a charge and refunds the retailer, the code says that money must be passed on in proportion to how your bills were affected.

A site whose rainwater never reaches a public sewer may be paying for drainage it doesn’t use, and a water audit can check that.

It might. A meter swaps a fixed charge for one that follows use, so a lightly used office could pay less while a busy kitchen could pay more.

The meter belongs to the wholesaler and you ask for one through your retailer. Terms differ by area. Severn Trent’s 2026/27 scheme says a retailer can ask for a meter to be installed at no charge, covering a single meter fitted externally at the boundary, with a quote for anything beyond that and a target of 22 working days. Yorkshire Water’s scheme lists a charge for a standard installation. Bristol Water charges a survey fee and quotes for the work.

Before asking, estimate your yearly use and set it against the annual unmetered charge, then ask your retailer what installation would cost and whether the change could be reversed. The business water meters guide covers the practical side.

1. Ask for a breakdown. Write to your retailer and ask for the RV or assessed basis it holds, the annual charge for each service, the days billed and the dates of any adjustment.
2. Raise a complaint if it isn’t resolved. CCW says the company should respond within 10 working days, and within another 10 at stage two.
3. Go to CCW. You can take it to CCW once you have a final response, or after eight weeks.
4. In Scotland, unresolved complaints go to the SPSO. Challenges to the RV itself go to the Assessor.

The complaints guide covers each stage.

We’d check the RV or assessed basis your retailer holds and whether each line matches a service your site actually receives. Then we’d go through the billing periods, day counts and any adjustments, so you can see which movement is arithmetic and which needs raising. If drainage looks questionable, a water audit can check whether you’re paying for drainage you don’t need. Where a meter might suit the site, we’ll help you put the question to your retailer.

Want a quote? An address and SPID are enough to compare business water suppliers.