Allan started his career with hometown club York City aged eight and had a loan spell with Hucknall Town of the Northern Premier League Division One South in 2011.

[4] He signed for Northern Premier League Division One South club Hucknall Town on loan in October 2011, making his only appearance as a substitute against Stamford before returning to York in November.

[8] He joined Conference North club Harrogate Town on a one-month loan on 21 November 2013, having made four appearances for York up to that point in 2013–14.

[10][11] Allan came on as an 89th-minute substitute for Will Hayhurst in York's 0–0 away draw with Fleetwood Town in the play-off semi-final second leg, resulting in the team being eliminated 1–0 on aggregate.

[16] Allan signed for newly relegated National League North club Alfreton Town on 6 July 2015 on a one-year contract.

[24] Allan missed the start of the 2019–20 season with a three-match suspension before joining York's divisional rivals Farsley Celtic on 16 August 2019 on a one-month loan.

[25] He made seven appearances for Farsley, scoring two goals,[10] and after returning to York went straight into the starting line-up for their 2–0 away win over Irlam in the FA Cup as cover for the injured Steve McNulty.

[10][32] York had finished in second place in the 2019–20 National League North on points per game after the season was suspended in March 2020 because of the COVID-19 pandemic in the United Kingdom[33] before being eliminated from the play-offs in the semi-final.