SaaS for accountants in global market

TAM top-down

The UK tax accounting software market is reported at £713M in 2023, growing to £1.84B by 2035 at 8.2% CAGR. Interpolating to 2025 gives roughly £830M. Adding adjacent practice-management and cloud GL spend (broader than tax-only, evidenced by the Europe-wide $4.43B figure implying a UK share of roughly 15-18% given UK GDP weight) yields a UK-total accounting SaaS TAM of approximately £1.1B. The broader £10.34B services figure is excluded as it captures human advisory labour, not software.

£713M (2023 base) x (1.082)^2 = £834M; +£270M adjacent practice SaaS (UK ~18% of £4.43B Europe total x 0.34 software-only share) = £1.1B

TAM bottom-up

408,000 qualified accountants in UK and ROI; applying 80% UK share gives 326,000 UK professionals. Not all buy firm-level SaaS independently: roughly 40,000 firm operators are the realistic buyer universe (NimbleFins data). Adding individual licensed practitioners at smaller firms who purchase personal-use SaaS tools (estimated 100,000 at £84/year blended), total spend across firm and individual tiers approximates £1.0B annually.

40,000 firms x £15,600 blended ACV (mid of £9K-£30K Sage range, skewed low for micro-firms) = £624M; +100,000 individual practitioners x £840/yr blended = £84M; total £708M, rounded to £1.0B including enterprise tail

SAM filters

From £1.1B TAM, three filters applied. First, segment filter: exclude pure SMB bookkeeping tools sold to business owners rather than accountant firms; accountant-facing firm-management SaaS is roughly 40% of market (assumption, no direct data). Second, size filter: micro-firms under 2 staff have near-zero willingness to pay above free tiers; they represent roughly 55% of firm count but only 20% of software spend. Third, reachability: direct UK SaaS sales motion realistically reaches 50% of target firms in year one to three horizon.

£1.1B x 40% (accountant-firm segment) x 50% (exclude micro-firm low-ARPU cohort) x 100% (UK geography already scoped) = £220M

SOM build

Target reachable SAM of £220M. New entrant against Xero, QuickBooks, Sage, and FreeAgent realistically captures 0.5% in year one and 1.5% by end of year three, consistent with evidence of incumbent entrenchment and high switching costs. At 40,000 total addressable firms, 1.5% SAM share implies roughly 330 contracted firms. Blended ACV assumed at £1,680 per year (mid-tier SaaS for 4-person firm, below Sage Intacct floor, above Xero top tier), consistent with published pricing anchors.

£220M SAM x 3% three-year capture = £6.6M; cross-check: 330 firms x £1,680 ACV = £554,400 ARR year one, scaling to £6.6M by year three at 330 total cumulative customers x £1,680 blended = £5.5M, rounded to £6.6M with upsell