Cleaned address file
CSV, Excel, JSON or a load into your CRM staging table, in the column layout your import or mailing house expects.
PAF address cleansing and postcode validation
Address Cleansing Services UK
Send us the address file that keeps bouncing mail, failing lookups or double-counting customers. We validate every postcode, standardise addresses to Royal Mail PAF conventions and merge records that point to the same delivery point, with a row-level record of every change.
99.8%Accuracy rate
48hrTypical turnaround
£0.25Per record
Why addresses break
What address cleansing is, and why the postcode field fails first
Address cleansing is the work of checking each postal address in a file against the UK's address rules and reference data, correcting what can be corrected, and setting aside what can't. A correctly formatted UK postcode narrows an address to around 15 properties, which is why so much depends on it: mailing runs, delivery routing, territory reports, gift aid claims and customer matching all key off that one field. It is also the field most often corrupted by hand entry, form validation that strips spaces, and exports that change the case.
Royal Mail's Postcode Address File (PAF) holds roughly 30 million delivery points and is updated monthly. It is the reference we clean against.
What we fix
The address errors we find in most UK files
Postcode format and spacing
SW1A1AA, sw1a 1aa and SW1A 1AA are the same postcode, but case-sensitive lookups treat them as three. We uppercase, trim and put the single space back between the outward and inward codes, then check the result against the valid postcode patterns.
Character confusion
The letter O typed for a zero, or a lower-case L for a capital I, produces postcodes that look right and fail every lookup. When a postcode fails validation we test the likely substitutions and re-check, rather than discarding the record.
Placeholder and fake postcodes
AA1 1AA, XX1 1XX and ZZ1 1ZZ pass a format check but point nowhere. They usually come from customers skipping a mandatory field. We catch them on the reference lookup and flag them, so they stop counting as valid addresses.
Address standardisation
Thoroughfare, locality, town and county arrive in the wrong columns, abbreviated three different ways, or all crammed into line one. We split and standardise them to PAF conventions so the address prints correctly on a label and matches on a join.
Duplicate addresses
"Flat 2, 14 High St" and "14 High Street, Flat 2" are one household. We match on the standardised address and the delivery point it resolves to, not on raw text, and merge duplicates under rules you sign off.
PO Boxes, BFPO and partial postcodes
PO Box and BFPO addresses are valid but are not physical locations, and some files hold only the outward code on purpose. We identify all three and mark them separately, so routing and geographic analysis use real premises only.
How it works
How we clean an address file
Every rule is written down and agreed with you before it runs, and it runs against a copy of your file.
01
Normalise
Uppercase postcodes, trim whitespace, fix the internal space and split address lines into consistent fields.
02
Validate format
Check every postcode against the valid UK patterns and mark the ones that fail.
03
Repair
Try the O/0 and I/1 substitutions on failing postcodes, then validate again.
04
Look up
Confirm passing postcodes and addresses against PAF-based reference data and return the standardised address elements.
05
Flag exceptions
Anything that fails every step goes to a rejects file with a reason code for a person to decide, not an algorithm.
Before & after
What a cleaned address file looks like
Illustrative layout only, not client data.
Before (placeholder)
address postcode 14 high st, flat 2 sw1a1aa Flat 2 14 High Street SW1A 1AA 1 Example Rd E1O 7AA Unit 3 ZZ1 1ZZ
After (placeholder)
address postcode status Flat 2, 14 High Street SW1A 1AA merged (2) 1 Example Road E10 7AA repaired O→0 Unit 3 ZZ1 1ZZ rejected: placeholder
Deliverables
What you receive
Before/after diff
Every changed address at row level: the old value, the new value and the rule that changed it.
Rejects file
Addresses we could not confirm, each with a reason: postcode not found, placeholder, ambiguous match, PO Box.
QA report
Valid postcode rate before and after, duplicates merged, repairs made and the sample checks we ran.
Repeatable script
The agreed rules as a script, so the next export cleans the same way without the setup cost.
Wider data cleaning
Emails, phone numbers and names in the same file can go through our data cleaning service in the same job.
Who it's for
Where clean addresses pay off
Direct mail and fundraising
Fewer returns, no duplicate households receiving the same pack twice, and gift aid declarations that carry a valid postcode. See our charity data cleansing guide.
E-commerce and delivery
Customer addresses that route first time, and delivery postcodes you can trust for zone pricing.
CRM migrations
Addresses standardised and deduplicated before import, so the new system starts clean. See data cleaning for CRM migration.
Property and territory data
Listings, branches and sales territories mapped to real postcodes, ready for geographic analysis.
Pricing
Address cleansing pricing
Address verification sits in our Professional Cleaning tier at £0.25 per record, which also covers deduplication, standardisation, phone validation and quality scoring. Ongoing runs and API integration are quoted on the Enterprise tier. Full tier details are on the data cleaning pricing table, and every job is quoted at a fixed price before work starts.
Questions
Frequently asked questions
What is address cleansing?
Address cleansing checks each postal address in a file against UK address rules and reference data, corrects formatting and postcode errors, merges duplicate addresses and sets aside the ones that cannot be confirmed. The result is a file where every address is either verified or flagged with a reason.
Do you check addresses against Royal Mail PAF?
Yes. Postcodes and addresses are confirmed against PAF-based reference data, Royal Mail's file of around 30 million UK delivery points, and standardised to PAF conventions for thoroughfare, locality, town and county.
Can you fix postcodes that fail validation?
Many of them. The common failures are missing or doubled spaces, lower-case letters and character confusion such as the letter O typed for a zero. We repair those and re-validate. Placeholder postcodes like ZZ1 1ZZ and postcodes that do not exist go into a rejects file with a reason code.
What is the difference between a UDPRN and a UPRN?
A UDPRN is Royal Mail's reference for a single delivery point in PAF. A UPRN is the Ordnance Survey reference for any addressable location, including places PAF does not cover. For commercial customer data the delivery point is usually the more useful key; UPRNs are more common in local government and housing data.
How much does address cleansing cost and how long does it take?
Address verification is part of our Professional Cleaning tier at £0.25 per record. Standard jobs are usually back within 48 to 72 hours; larger or messier files can take one to two weeks. We give a fixed quote and timeline after profiling a sample.
Further reading
Guides on UK address data
Send us a sample of your address file
Tell us the record count and what the addresses are used for. We will profile a sample and come back with the rules, the price and the turnaround.