Neither Big Four nor Tier-2 firms publish due diligence fees, so the premium can only be measured on your own competing quotes, compared hour by hour and grade by grade. The judgement is whether the buyer's IC, lender or LP will discount the deliverable if it does not carry a Big Four badge.
The honest take
Big Four scope is genuinely worth the premium on three profiles: multi-jurisdiction tax structuring across more than three tax-residence countries, FCA-authorised or regulated targets where supervisory-correspondence interpretation is on the critical path, and carve-out FDD where stand-alone-cost modelling demands operational-DD bench. Outside those, a Tier-2 report is often all the deal needs; put both proposals side by side on hours, grades and named team before deciding.
Side by side
Deloitte UK
Big Four
Big Four house with full Strategy and Transactions team. Anchors on £50m+ EV deals, regulated targets, cross-border and carve-out complexity.
Sectors: Financial services, TMT, Energy, Healthcare, Infrastructure
Pricing: Quote-only. No published rate card. Ask for hours by grade and the rate per grade so the quote can be compared with a Tier-2 proposal.
Adviser profile ->Grant Thornton UK
Tier-2
UK Tier-2 firm whose transaction advisory services team carries out buy-side and sell-side financial and tax due diligence for private equity and corporate clients.
Sectors: Technology, Financial services, Consumer, Healthcare
Pricing: Quote-only. The firm publishes service descriptions, not fees or rate cards.
Adviser profile ->This page is anchored to UK primary legislation and named regulator guidance only. Not legal advice. Confirm position with your appointed adviser before signing.