The pattern
TikTok Shop seller with £180k GMV but only £128k landing in the bank after platform commission, affiliate fees, ad spend and refund credits. Previous accountant had filed VAT on the bank figure.
What gets done
Returns refiled with GMV as taxable turnover and the platform/ad/refund/affiliate items split into cost-of-sale ledgers. Net VAT bill higher by the corrected gross-vs-net difference, but the underlying P&L now passes an enquiry and the margin number is true.