SROI vs TOMs: what bidders need to know

The National TOMs framework works by assigning a published monetary proxy value to each unit of a specific social outcome. A commitment to deliver one apprenticeship year produces a proxy social value of £13,500. A local employment opportunity created has a proxy value of £12,654. These figures come from published datasets — the HACT Social Value Bank, the New Economy Unit Cost Database, and equivalent sources — and are maintained by the Social Value Portal.

To calculate a TOMs-based social value total, you multiply your committed quantity by the relevant proxy value: five training days at £320 each produces £1,600 of social value. The total across all your commitments gives the gross proxy social value figure. This gross figure is what most National TOMs evaluations compare between suppliers, alongside a credibility assessment of whether commitments are genuinely deliverable.

TOMs-based evaluations do not require SROI adjustments unless the buyer explicitly states otherwise. If the ITT references "National TOMs" or "proxy values" without mentioning deadweight, attribution, or displacement, a gross figure is the correct output. Applying SROI adjustments to a TOMs-only evaluation is unnecessary complexity that serves no purpose and may confuse evaluators.

SROI (Social Return on Investment) is a methodology that applies a more rigorous analysis to social value claims. Where TOMs produces a gross figure by multiplying quantities by proxy values, SROI requires three adjustments before a net social value figure can be stated. These adjustments reduce the claimed value to account for factors that would otherwise produce an inflated or misleading number.

The resulting SROI ratio expresses the net social value generated per pound of investment. A ratio of £4:£1 means that for every pound invested in the contract, £4 of net social value is generated. This ratio is calculated after applying deadweight, attribution, and displacement adjustments to the gross proxy value.

SROI is required when the ITT explicitly specifies SROI methodology, references a "net social value figure", or asks for deadweight, attribution, or displacement analysis. It is more common in NHS procurement and some housing association contracts than in standard local authority or central government procurement. If the ITT does not mention these adjustments, you are not required to apply them.

The ITT and any linked social value guidance documents should make the required methodology explicit. Phrases to look for: "National TOMs framework", "TOMs outcome measures", "proxy values" (suggests TOMs without full SROI); "SROI methodology", "net social value", "deadweight", "attribution", "displacement" (requires full SROI adjustments).

In practice, many buyers use language loosely. A buyer who asks for a "social return on investment" calculation may mean SROI in the technical sense, or may simply be asking for a monetised social value figure using proxy values — without expecting the full SROI adjustment methodology. When the ITT is ambiguous, err on the side of applying the adjustments: a response that demonstrates awareness of deadweight and attribution is more credible than one that does not, even if adjustments were not strictly required.

For a practical view of how proxy values work — whether or not you go on to apply SROI adjustments — see the social value calculator, which uses published National TOMs and Cabinet Office figures to produce a gross indicative total. HelpMeBid's full product applies SROI adjustments in the commitment builder, with transparent defaults sourced from published SROI guidance.

See also the social value glossary for plain-language definitions of SROI terms, TOMs terminology, and procurement framework language.