Throughout the year we continued to ensure customers received their social policy entitlements and tax refunds on time and supported customers to meet their tax obligations. We also issued automatic individual income tax assessments, implemented Stage 4 Release 1 of our transformation programme and actively contributed towards COVID-19 initiatives.
Our outcome performance has been strong in a year of significant events and challenges. We continued to provide customers with timely refunds and social policy payments and achieved all timeliness targets. Assessed tax revenue of $93.8 billion was 21% higher than in 2019-20. Business customers reported a significantly improved experience when dealing with us, with an 8-point increase in our score under the Ministry of Business, Innovation and Employment Better for Business Customer Experience Index from that in December 2019.
This was our third year of running automatic income tax assessments for individuals. We continue to look for ways to make tax simpler for New Zealanders by better using the data we hold. With more detailed and timely reporting of employment and investment income information, accuracy will continue to improve, and we should see the value of end-of-year income tax refunds and tax to pay reduce over time.
The average refund from these assessments has reduced each year, decreasing from $430 in 2019 to $394 in 2020. Provisional results for 2021 show a further $41 reduction from 2020 to $353.
Results from our impact indicators show that customers are increasingly using our online services, with an increase in the number of returns being filed digitally, and donation receipts and correspondence being sent digitally. We saw increases in on-time payment and return filing by customers. On-time payments increased by four percentage points to 89.9%, and on-time filing increased by over one percentage point to 94.3%. We also have a number of case studies that demonstrate that we’re realising the benefits of our transformation through how we are using our new START core system and analytical tools and capabilities.
We achieved 37 out of 44 or 84% of our output performance measures this year, a significant improvement on 2019-20 when we achieved 30 out of 45 or 67%. Half of our output measures show improved performance in 2020-21, demonstrating our focus on delivering quality services to customers.
We deferred some debt activities where customers needed a different kind of support from us due to the economic impact of COVID-19. This change of focus impacted on our performance measures around the management of unfiled returns and debt.
We’re progressing our environmental sustainability strategy to deliver on the 2025 carbon neutral target set by Government. We have reduced our fleet and purchased 28 electric vehicles to replace petrol-based vehicles, meaning a third of our fleet is now electric. Our levels of CO2 emissions and printer use dropped significantly this year, as we worked more flexibly, enabled by our technology. Our facilities asset performance results have been affected by COVID-19 as we have been unable to complete some of the required checks on buildings and vehicles.