Agency and consultant expenses in the UK: SaaS reverse charge, IR35, and home office

An agency’s cost base looks nothing like a shop’s: the biggest lines are people and software, and much of the software is bought from companies based abroad. That shifts two questions to the centre of the books: how VAT works on overseas services, and how the people you pay are classified for tax. Get those right and the rest of agency accounting is ordinary. All figures below are sourced from HMRC guidance in the Sources section.

Overseas software and the reverse charge

Design tools, cloud hosting, ad platforms, and analytics are usually billed from outside the UK. For a VAT-registered business receiving general-rule B2B services from an overseas supplier, the supply falls under the reverse charge: you act as both supplier and recipient, crediting output VAT and debiting the same amount as input tax on your own return ^[1] .

The practical trap is treating a no-VAT overseas SaaS invoice as if it carried reclaimable UK VAT, or omitting the reverse-charge entry entirely. Neither matches the return HMRC expects.

Contractors, freelancers, and IR35

Agencies lean on freelancers, and the off-payroll working rules (IR35) decide whether a contractor working through their own company is taxed like an employee. The rules apply when the worker would have been an employee if engaged directly ^[2] . For public sector and large or medium private clients the client determines status; crucially, an agency in the supply chain can become the party responsible for deducting Income Tax and National Insurance ^[2] .

So a contractor invoice is not always just a cost to book: it may carry a status determination and payroll obligation. HMRC’s Check Employment Status for Tax (CEST) tool supports the determination ^[2] .

Home office and other costs

Most agency principals work partly from home. Claim it with HMRC’s simplified flat rate or by apportioning actual costs, as covered in the claim home office in the UK guide. Professional indemnity and public liability insurance taken out for the trade are deductible. Client travel and subsistence follow the claim travel in the UK and claim business meals in the UK guides, remembering that entertaining clients is blocked.

Advertising spend and platform fees

The other large overseas line for most agencies is paid media: Google, Meta, LinkedIn, and similar ad spend, much of it billed from outside the UK. The same reverse-charge logic applies to those advertising services as to software, so a no-VAT ad-platform invoice is a self-account, not a reclaim against the supplier. Agency commissions you charge clients on that media are your own standard-rated supply and are separate from the cost of the media itself, so keep the pass-through media spend and your fee distinct in the ledger or the margin reporting blurs.

Registration and Making Tax Digital

A growing agency must register for VAT once taxable turnover passes the registration threshold, and once registered it keeps digital records and files under Making Tax Digital for VAT. The reverse-charge entries above flow through the same return, so getting the bookkeeping right at capture is what keeps the quarterly filing clean. The UK VAT and MTD guide covers the filing mechanics.

Where ExpenseFlow fits

An agency ledger is dominated by recurring software subscriptions and contractor invoices, many from overseas. ExpenseFlow captures each receipt and supplier invoice, extracts the line detail and the currency, and syncs the transaction into Xero or QuickBooks Online with the source image attached for the six-year record-keeping window. Its cross-border checks flag a purchase from an overseas supplier that has not charged UK VAT, so it is recorded as a foreign-currency cost that may belong on the reverse charge rather than wrongly treated as carrying reclaimable input VAT, and it flags contractor and freelancer payments so the off-payroll (IR35) status question is raised at capture rather than missed. It does not make the IR35 status determination, run payroll, or apportion your home-office costs: those stay with you or your accountant. What it removes is the manual keying behind a high-volume subscription and contractor ledger.

Common mistakes

• Treating a no-VAT overseas SaaS invoice as carrying reclaimable UK VAT, or skipping the reverse-charge entry ^[1] .
• Booking a contractor invoice as a simple cost when an off-payroll status determination and deduction may apply ^[2] .
• Claiming entertaining clients as a deduction (it is blocked), while missing the allowable home-office and subsistence claims.
• Losing the policy schedule that supports a professional indemnity insurance deduction.