Introduction The Index of Orthognathic Functional Treatment Need (IOFTN) was developed to measure functional difficulties arising from malocclusions related to facial deformity. The IOFTN is not currently being used to determine suitability for orthognathic treatment, however, it is a useful aid for assessing and referring patients and takes into account functional and facial appearance. This paper aims to evaluate the potential impact of introduction of the IOFTN on the future provision of orthognathic services.Methods Two methods were used to consider the impact of the IOFTN on orthognathic provision. Firstly, a local retrospective audit was undertaken in Leeds Teaching Hospital NHS Trust involving thirty consecutively treated patients, for whom full records were retrieved. Data was collected using a standardised data caption form. Local standards were agreed concerning the need for treatment. Secondly, a systematic search of published studies was completed to assess evidence from across the UK.Results The audit standard, that is, 90% of patients treated with orthognathic surgery should be categorised as grade 4 (great need) or 5 (very great need) using the IOFTN, was fulfilled. The most common reason for seeking treatment related to dental and facial aesthetics and no patients were treated for speech or TMJ problems alone. The systematic review searches identified four suitable records for inclusion in the review, including two audits and two retrospective studies undertaken in secondary care settings across England and Scotland. These studies showed that at least 86% of all participants scored 4 or 5 using the IOFTN.Conclusions The findings from the audit and literature review indicate that referrals from general dentists and acceptance for orthognathic treatment in secondary care is unlikely to be significantly affected by introduction of the IOFTN. Referring dentists may find the IOFTN a useful prompt for determining whether people are suitable for orthognathic treatment.