Fee dispute and professional conduct: ARB Code 2025

You are a sole practitioner architect. Eight months ago you completed the design and planning stages (RIBA Stages 1 to 4) of a private residential extension for a returning client under a RIBA Concise PSC 2020. The fee was agreed at £22,000, invoiced in four stage payment milestones. You submitted your final Stage 4 invoice (£6,500) two months ago. The client has not paid and has now written to you claiming that you significantly over-claimed on the Stage 3 milestone, which they believe was only 60% complete when you invoiced 100%. They are withholding both the Stage 3 balance and the Stage 4 invoice, totalling approximately £9,800. In the same letter, the client states that they have written to the ARB expressing concern about your billing practices. The client's letter also hints, without explicitly saying so, that they may be prepared to pay if you agree to provide additional services (finalising the tender package for the main contractor) at no extra charge. You had not agreed to provide this service and it is outside the scope of your RIBA Concise PSC 2020.