Institutional investors hold
a different standard.

At Series B, the financial requirements shift significantly from Series A. Institutional investors expect audited or audit-ready financials, a robust governance framework, detailed cohort analysis across 24 to 36 months, and a financial model that withstands institutional scrutiny. A fractional CFO at Series B builds all of this infrastructure, leads financial due diligence, supports the VDD process, and ensures the company can defend every assumption in the model.

Series B due diligence is typically led by institutional investors with dedicated finance teams and forensic financial advisers. It is far more intensive than Series A. Investors will rebuild your metrics from source data, stress-test every model assumption, scrutinise revenue recognition policies, and examine the consistency of your financial reporting over 24 to 36 months. Any inconsistency in how metrics have been calculated historically becomes a significant red flag. Preparation must begin at least 6 months before launch — ideally 12 months.

Most UK SaaS companies do not need a full-time CFO until they have closed a Series B and are scaling rapidly toward £10m to £15m ARR. Before that point, a senior fractional CFO provides the same strategic capability at a fraction of the cost. The trigger for a full-time hire is typically headcount above 80, international expansion requiring local statutory compliance, or an imminent IPO preparation process.

A VDD report is a financial due diligence report prepared by the company — or their advisers — in advance of a fundraise. It covers quality of earnings, revenue recognition, metrics validation, and working capital analysis. At Series B, institutional investors expect a VDD report. It removes information asymmetry, accelerates the due diligence process, and demonstrates the financial maturity investors expect at growth stage.

There is no fixed ARR threshold, but most UK SaaS Series B rounds are raised at £3m to £15m ARR. More important than the absolute ARR figure are the growth rate, NRR, gross margin, and the evidence of a repeatable, efficient growth engine. A company at £4m ARR growing 80% year-on-year with 120% NRR will typically attract better terms than one at £8m ARR growing 30% with 95% NRR.