Company lists · Data refreshed September 2026
Top 25 Accounting software integration firms based in the United Kingdom
RevenueBase identified 335 accounting software integration firms headquartered in the United Kingdom as of September 2026 and tracks 3,731 professional contacts across them, including 1,163 with verified work emails. London is the largest hub.
This list covers accounting software integration firms headquartered in the United Kingdom, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed September 27, 2026.
Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.
The 25 largest accounting software integration firms based in the United Kingdom
Ranked by team size| # | Company | Contacts | |||
|---|---|---|---|---|---|
| 1 | 477 contacts → | ||||
Partial evidence “Outbooks is a leading provider of outsourcing services to accounting and bookkeeping firms.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 2 | 304 contacts → | ||||
Partial evidence “Here at Aptitude, we provide software solutions to enable deliver fully autonomous finance so our customers can drive growth, efficiency and sustainability.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 3 | 156 contacts → | ||||
Partial evidence “Inflo transforms the accounting profession by making leading-edge technologies accessible to all.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 4 | 133 contacts → | ||||
Indirect evidence “Traditional accountants do a great job of the numbers, but that's often as far as the service goes.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 5 | 101 contacts → | ||||
Partial evidence “The complete tax and accountancy practice software suite, powered by a single database.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 6 | 81 contacts → | ||||
Strong evidence “Capium is an online accounting & practice management software, tailored specifically for accounting practices.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 7 | 64 contacts → | ||||
Indirect evidence “At Eureka Solutions, we specialise in implementing powerful cloud-based systems that have the potential to revolutionise your business.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 8 | 61 contacts → | ||||
Indirect evidence “We help businesses do more than just balance the books.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 9 | 58 contacts → | ||||
Indirect evidence “We are on a mission to help accountants to grow their accountancy practice and become more profitable.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 10 | 51 contacts → | ||||
Indirect evidence “Empowering Businesses to Thrive Through Financial Clarity | Adroit Accountax We're a team of passionate and experienced accountants dedicated to your business success.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 11 | 50 contacts → | ||||
Strong evidence “Quill offers legal accounting, practice and document management software for the smart law firm.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 12 | 44 contacts → | ||||
Indirect evidence “Big enough for best-in-class support but small enough for your undivided attention, itas invests in your long-term success.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 13 | 43 contacts → | ||||
Partial evidence “ION implements cloud accounting solutions into Education, high-growth and PE-backed organisations.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 14 | 42 contacts → | ||||
Indirect evidence “You run an accountancy practice.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 15 | 42 contacts → | ||||
Strong evidence “IRIS is a long-established industry leader in accounting software and services for accountants and bookkeepers.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 16 | 41 contacts → | ||||
Strong evidence “Pegasus Software is one of the UK's leading suppliers of accounting software, cloud accounting software, business solutions and payroll software and has been for over 30 years.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 17 | 35 contacts → | ||||
Partial evidence “At Acting Office we deliver a fully integrated software platform designed for modern accountancy practices that want precision, efficiency and complete visibility across their…” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 18 | 34 contacts → | ||||
Partial evidence “Codis are a successful and well established business software developer.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 19 | 32 contacts → | ||||
Strong evidence “Ember is a specialist accounting and tax software platform and was acquired by Starling Bank in 2025.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 20 | 30 contacts → | ||||
Indirect evidence “We found that there was often a breakdown in service between your bookkeeper and your accountant and that more often than not the accountant was spending a majority of their time…” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 21 | 29 contacts → | ||||
Indirect evidence “Our clients rely on us to remove book-keeping hassle and improve their profitability by using our top quality financial reports based on professionally reconciled book-keeping.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 22 | 26 contacts → | ||||
Indirect evidence “We connect your CRM, ERP, AI and Cloud systems, bridging internal platforms and external tools so your data flows cleanly, your processes run automatically, and your business…” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 23 | 25 contacts → | ||||
Strong evidence “Zynk is one of leading Integration Platform as a Service providers specializing in accounting data integration.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 24 | 23 contacts → | ||||
Strong evidence “Founded in 1982, Castle Computer Services provides accounting and financial management software, business intelligence solutions, cloud and managed IT services throughout the UK…” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
| 25 | 22 contacts → | ||||
Indirect evidence “A leading Sage X3 and Sage Intacct Business Partner.” Source: RevenueBase Database · checked Sep 27, 2026Thanks. The Data Team will review it. | |||||
RevenueBase Smart Search
RevenueBase Smart Search assesses information from a company’s LinkedIn profile, information supplied directly by the company, its website, and other publicly available sources. It uses that information to rate how closely the company relates to this list’s category: accounting software integration firms. Every row carries its rating and the description the rating was read from, so each one can be checked rather than taken on trust.
- Strong evidence
- The company's own public description of its business names accounting software integration firms.
- Partial evidence
- Its own public description names part of accounting software integration firms, so it works in or next to the category without describing itself that way.
- Indirect evidence
- The description shown does not name accounting software integration firms. The match rests on the rest of the company's public profile rather than the one sentence quoted here, so this is the rating to check first.
RevenueBase Smart Search is how these lists are built: RevenueBase's data engine and AI assemble the companies that match a category defined in a user's own words, so a list can be about what companies actually do rather than about whichever industry code they were filed under.
Showing 25 of 335 accounting software integration firms based in the United Kingdom
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Accounting software integration firms based in the United Kingdom at a glance
As of Sep 27, 2026Companies by employee count
Email recency for this list is measured worldwide rather than for United Kingdom, so it is reported there. Company counts and contact totals on this page are exact for United Kingdom, over 335 companies.
How this list was built
Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among accounting software integration firms, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.
- Source
- The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
- What qualifies
- Companies headquartered in the United Kingdom whose own description of what they do matches “accounting software integration firms”. Matching reads each company's description, not its industry code or its name.
- RevenueBase Smart Search
- RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names accounting software integration firms), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
- What we exclude
- Companies whose own description does not clearly place them among accounting software integration firms, and records with no verified work email. Companies headquartered outside United Kingdom are excluded even when they keep an office there.
- Match quality
- In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
- Ranking
- Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
- Verification
- Every listed company carries at least one verified work email, 1,163 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
- Refresh
- This page's figures were pulled from the company graph on September 27, 2026. Lists refresh periodically as the graph is re-checked.
- Corrections
- Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.
Accounting software integration firms by metro
- Accounting software integration firms in London84
Frequently asked
What is RevenueBase Smart Search?
RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names accounting software integration firms, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.
How many accounting software integration firms are there based in the United Kingdom?
RevenueBase identified 335 accounting software integration firms headquartered in the United Kingdom as of September 2026, matched on each company's own description of what it does rather than its industry code.
What is the largest company on this list?
Outbooks, headquartered in London, tops this list with the largest team on record.
Which city has the most accounting software integration firms?
London leads with 84 headquartered companies, followed by Manchester (11) and Bristol (8).
How do I get contact information for these companies?
A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 1,163 verified decision-maker contacts tracked across these 335 companies.
How current is this list?
The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 27, 2026.
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About this data
RevenueBase is a B2B data infrastructure company. Its company graph covers 60 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.
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