Two close-out recommendations distinct from general small-business admin: get business insurance, and hire an accountant who specializes in Amazon FBA specifically (not a generalist), paired with a connector tool like Link My Books to reconcile Amazon settlement data into standard bookkeeping software.
The reasoning is that Amazon settlement reports (FBA fees, referral fees, storage fees, reserves, VAT-on-fees) don't map cleanly onto standard invoice-based bookkeeping, so a generalist accountant without FBA-specific experience tends to misclassify or miss deductible fee categories.
Apply: set this up once the business has live sales, not upfront — but flag it during the business-formation step (Amazon FBA Business Formation Checklist (UK)) so books are FBA-structured from month one.
"A general accountant is no good" — Amazon FBA's accounting needs (COGS by SKU landed cost, FBA fee categorization, VAT/sales-tax nexus, inventory valuation) are specific enough that a generalist accountant without e-commerce experience will typically misclassify or miss them, reinforcing why the stack calls for a specialized accountant rather than a general-practice one.