The firm provided event and project management services and its clients included Air New Zealand, Russell McVeagh, and Datacom Group.

[5] She was selected as the party's Taupō electorate candidate in 2008 where she unseated Mark Burton, a Labour cabinet minister who had represented the area for 15 years.

[14] During the 2011 New Zealand general election, Upston retained Taupō by a margin of 14,115 votes, defeating Labour candidate Frances Campbell.

[11] During the 2014 New Zealand general election, Upston retained Taupō by a margin of 15,406 votes, defeating Labour candidate Jamie Strange.

[19] The following month, she attracted criticism for refusing to comment on women's rights in the workplace after it was revealed Prime Minister John Key was forced to apologise to a Parnell cafe worker for repeatedly pulling her hair.

[20] She attracted further scrutiny in the portfolio for rejecting calls to remove GST on menstrual products and for refusing to comment on an incident involving the mistreatment of a stripper by Chiefs ruby players.

She was also spokesperson for land information, social investment and whānau ora (2020–2021), employment (2020–2023), regional economic development (2021), child poverty reduction (2021–2023), and family violence prevention (2023).

[11] During the 2017 New Zealand general election, Upston retained Taupō by a margin of 14,335 votes, defeating Labour candidate Ala' Al-Bustanji.

Upston began working on the bill in 2010 after being contacted by a constituent whose brother was murdered and whose killer was found not guilty by reason of insanity.

[38][39] The bill proposed that, even if they unable to be found guilty of a crime, the court may find an offender has been proven to have acted grievously.

[38][40] During the 2020 New Zealand general election, Upston retained Taupō by a margin of 5,119 votes, defeating Labour candidate Ala' Al-Bustanji.

[41] As social development spokesperson, Upston promoted National's policy of harsher penalties for unemployed people on the jobseeker benefit including a mandatory reapplications every six months, increased use of stand-downs from receiving welfare, and greater direct management of beneficiaries' incomes by the Ministry of Social Development.

While ruling out minimum wage increases and student allowances for high schoolers, Upston advocated tax cuts, rebates and helping their parents find work as a means of improving school attendance and educational performance.

[47] In early April 2024, Upston confirmed that the Government and the University of Auckland were exploring options to continue funding the Growing Up in New Zealand longitudinal study.

[50] On 24 July, Upston's absence from a Parliamentary sitting led to the withdrawal of the Government's Regulatory Systems (Social Security) Amendment Bill.

Following the incident, Upston confirmed that the Regulatory Systems (Social Security) Amendment Bill would be taken back to the Business select committee and reintroduced at a later stage.

Key changes have included extending the benefit sanctions period from one year to two years, requiring Jobseeker beneficiaries to apply every six months, requiring beneficiaries with work obligations to create a jobseeker profile, creating a special payment card for accessing a limited ranges of products and services and new community work sanctions.

Upston also promised that the rule of preventing sanctions from cutting benefit pay by more than 50 per cent of job seekers who had children would remain in place.