OBJECTIVES:  The role of the National Centre for Pharmacoeconomics (NCPE) is to evaluate cost-effectiveness and budget impact of all new medicines in Ireland. This is particularly relevant for high cost drugs reimbursed on the Community Drug Schemes where expenditure has risen from €315m (2009) to €485m (2014). The objectives of this study were to analyse the quality of budget impact models submitted to the NCPE for high cost drugs and to examine the difference in actual versus company-predicted expenditures. METHODS:  Quality was assessed using five criteria from NCPE submission guidelines. These consist of eligible population, gross and net budget impact, additional costs and offsets and sensitivity analysis. Quality scores were rated from one to five. Drugs which were reimbursed under the high-tech drug scheme between 2013 and 2015 were included. Actual expenditure data was extracted from the Health Service Executive- primary care reimbursement service database and compared with forecasted figures from company submissions. Submissions without budget impact information were excluded. RESULTS:  Eighteen drugs were included in the quality assessment:11 were rapid review submissions and 7 were full pharmacoeconomic assessments. The average score for rapid reviews was 44%. Full evaluations scored 91%. Eighteen drugs were included in the expenditure analysis. Nine companies underestimated the budget impact and nine overestimated. The cumulative expenditure on these drugs between 2013 and 2015 was €47.3 million compared with an estimated expenditure of €42.3 million representing an overall underestimation of €5.03 million in company submissions. The most significant overestimate was €2.6 million and related to a drug for pulmonary arterial hypertension. The biggest underestimate was €3.5 million for a prostate cancer treatment. CONCLUSIONS:  Guidelines relating to budget impact for rapid reviews need to be implemented to ensure greater consistency in quality of submissions. A reduction in ambiguity may limit the discrepancies between predicted and actual budget impacts.