How to Build a SaaS Product in the UK — From Architecture to Launch (2025)

A SaaS MVP: £35,000–£50,000. A full B2B SaaS platform with billing, user management, and APIs: £60,000–£150,000. Enterprise SaaS with SSO, audit logs, and compliance certifications: £100,000–£200,000+. Most SaaS builds qualify for HMRC R&D Tax Credits (up to 27% back) if they involve novel technical approaches.

You are a data processor for your customers. Required: an Article 28 Data Processing Agreement (DPA) in your terms of service, UK-region data hosting (AWS eu-west-2 or Azure UK South), data subject rights implementation at tenant level (customer must be able to request deletion), Article 30 records of processing, and a Privacy Notice covering your own data collection from users.

Stripe for B2C and most B2B (card payments, Apple Pay, Google Pay, wide international support). GoCardless for B2B where direct debit is preferred (lower transaction fees at scale, higher success rates than cards — cards expire, bank accounts don't). Many B2B SaaS products offer both. GoCardless requires UK bank account from customers; Stripe works globally.