Understanding Society: the UK Household Longitudinal Study is the largest household panel study in the world, designed to address key scientific and policy questions of the 21st century. It collects high quality annual longitudinal data on individuals of all ages in households representative of the UK population. Such data enable researchers to explore the experiences, causes and consequences of changes in people's lives - their family structure, health, income, expenditure, employment and housing. The Study has additional samples for the detailed exploration of the circumstances of key immigrant and ethnic minority groups; and collects data on cognition, objective measures of health and genetics to understand how people's health and wider circumstances interact. Increasingly we have been able to secure linkage to contextual information for places and organisations, and with consent, to individual level data including administrative records, social media and commercial information. Additionally, the Study experiments with innovative ways of collecting data to continually improve the content and quality of data available. Finally, we invest in supporting researchers and working with policy makers to ensure the research based on these data is used to inform policy and practice. The Study began in 2008 with the Innovation Panel (IP), which tests methods, and the first main wave of fieldwork started in 2009. It builds on and incorporates the British Household Panel Survey (BHPS), which means for some families we have annual information from 1991. To date, seven waves of the main Study and nine waves of the IP, as well as data collected from a nurse visit, are deposited in the UK Data Service. Data collection and planning are ongoing for Waves 9-11 and IP11-12; IP10 and Wave 8 data will be released in 2018. This bid covers the costs of data collection for Wave 12 of the main Study and IP13 and 14, and associated activities. In Wave 12 we will continue to push web-first data collection within our mixed mode framework to reduce costs while maintaining response rates and data quality. We are funding Methodological Fellowships to support this. Additionally, in IP13 and 14 we will experiment with other ways of collecting and harvesting data - for example between-wave surveys, apps, scanning till receipts - to expand the research opportunities available. We are also reaching out to other potential respondents: those whom we lost in BHPS where we can find them, and the partners of people in the Study who do not live in the same households. Finally, we will be trying to understand why people who emigrant do so by interviewing such groups as they leave the Study, and also we will interview family members when a respondent moves into a care home. Policy and research agendas are constantly evolving, and it is important in a longitudinal study to balance creating long series of the same data with including new questions that address emerging topics. For Wave 12 we are reviewing whether our survey adequately captures the way in which technology impacts on different aspects of our lives. We have appointed a number of experts - Topic Champions - to improve the content of the survey and the way we present the data to users. We also aim to focus on developing our content in childhood, which is limited at present. Supporting researchers in universities, government, third sector and businesses to use the data effectively is fundamental to the success of the Study. We have a Policy Unit that directly works with government departments and third sector organisations to help them use Understanding Society data, and we undertake a wide range of activities to promote findings based on the Study to policy users. We are planning a range of international events to promote effective comparative research, especially in relation to policy analysis using the Study. We are also funding Policy Fellowships to promote the policy impact of the Study.