Background Pharmaceutical companies make hundreds of millions of pounds in marketing/R&D-related payments annually to healthcare organisations and healthcare professionals. UK pharmaceutical industry self-regulatory bodies require member companies who sign up to their code of conduct to publish details of their payments. They are also required to publish the methodologies underlying these payments - methodological notes. This study aimed to analyse UK pharmaceutical companies' methodological notes and their adherence to the relevant codes of conduct and guidance. Methods We conducted a content analysis of methodological notes for the years 2015, 2017 and 2019 and assessed companies' adherence to self-regulatory bodies' requirements and recommendations for methodology disclosure. Results Overall, 90 companies made payment disclosures in all three years, publishing 269 methodological notes. We found gaps in adherence to self-regulatory requirements. Only 3 (3.3%) companies provided clear information for all self-regulatory body recommendations and regulations in all of their notes. Companies also varied in their approaches to important areas. For example, of the 244 notes with clear information on VAT management, 36.1% (N=88) included VAT, 30.3% (N=74) excluded VAT, and 33.6% (N=82) had multiple rules for VAT. Conclusions There was evidence of widespread non-adherence to self-regulatory requirements. This suggests flaws with self-regulation and a need for greater enforcement of rules or consideration of a publicly mandated disclosure system.

JL, PO, BM, ER, CK, MA, TF and FM have no competing interests. SM's partner is employed by ICON, a global Contract Research Organization whose customers include many pharmaceutical and medical device companies.

JL, ER, TF and FM received no specific funding associated with this publication. BM, SM and PO were supported by the grant 'Following the money: cross-national study of pharmaceutical industry payments to medical associations and patient organisations', awarded by The Swedish Research Council (VR), no. 2020-01822. CK and MA were funded by the RCSI Research Summer School. The funders had no role in study design; in the collection, analysis, and interpretation of data; in the writing of the articles; and in the decision to submit it for publication.

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