The move follows the trust's request to the Department for Transport to extend its underwriting for construction of the project through to September 2017.
If the DfT agrees to the request, taxpayers will be responsible for paying the trust's bills in the event that the project falls through. The funds are included in the original £30m which the DfT has allocated to the Garden Bridge.
However the DfT has not yet agreed to the request, with transport secretary Chris Grayling reportedly looking closely at the bridge's finances before committing funds.
The bridge aims to provide London with a new landscaped space over the River Thames, with extensive planting designed by Dan Pearson. Willerby Landscapes secured the landscape contract last year, with Palmstead Nurseries and Deepdale Trees to supply the plants.
The project was championed by former London mayor and Transport for London head Boris Johnson and former Chancellor George Osborne, but the election of new mayor Sadiq Khan and ministerial reshuffling by Prime Minister Theresa May means political backing for the bridge is no longer guaranteed.
Khan has expressed his support for the bridge but with reservations, and has said no more public money will be spent on the project.
Of the £60m of public funding that has been committed to the project, £20m is repayable as a loan to Transport for London (TfL). All public money must be used for pre-construction and construction work. In June the trust had spent just under £36m of the £36.4m of public funding received.
How the bridge could look in winter. Image: Garden Bridge Trust
A Garden Bridge Trust spokesperson said: "The Garden Bridge Trust currently has a year end date of October, which reflects the commencement date of the Trust. It has been decided to align the future year end to March which is a common year end date for charities.
"The new year end for the Trust will therefore be the traditional financial year end of 31 March. This will result in accounts being prepared for a 17 month period from 1 November 2014 to 31 March 2016."
The spokesperson added that the Garden Bridge Trust "has made great progress on the Garden Bridge this year with the discharge of planning conditions, ground investigation work taking place, agreeing logisticsand a construction programme, reaching agreements with key stakeholders involved in work on the Thames, as well as strong progress on private fundraising".
The new filing dates for the Garden Bridge Trust's accounts will be 31 December 2016 at Companies House and 31 January 2017 at the Charities Commission.
According to Charities Commission rules, a charity can change its year-end by informing the commission but the reporting period must not be less than six months or more than 18. Financial information must be sent within 10 months of the end of their financial year.
Charities Commission spokesman Joshua Snape said the commission had not yet been approached by the Garden Bridge Trust to change its year end, but the trust would need to do so.
Construction of the bridge was to begin this summer but has now been delayed until the autumn, raising concerns about a possible clash with the construction of the Thames Tideway Tunnel, a new "Supersewer" considered essential for the city's development.
The trust spokesperson said: "Construction is planned to start this year and we have been in extensive dialogue with the Thames Tideway Tunnel to ensure that our respective works are fully integrated with no construction clashes."