The state government of South Australia will be expanding the coverage and extending the deadline of the land tax relief for landlords as part of the economic stimulus amid the COVID-19 outbreak.

The scheme will be extended until the end of April next year and will now include eligible commercial owner-occupiers.

Under the scheme, landlords can apply for up to a 50% reduction on their land tax liability for the financial year 2019-2020. In return, landlords must pass on the full benefit to their affected tenants.

Treasurer Rob Lucas said by helping landlords, the state will also be able to help support tenants and ensure that local jobs are sustained amid the challenging economic environment.

"Rent can be one of the biggest fixed costs for a small business or residential tenant and this scheme complements the work of many landlords who have been working with their tenants and financial institutions to find an effective way through this period," he said.

The state government will also be extending some provisions of the COVID-19 Emergency Response Act — which were supposed to end this month — until March next year.

"Some provisions were set to expire by the end of September, when it's clear the impacts of the coronavirus are still being felt by families, businesses and the broader community," said State Attorney-General Vickie Chapman.

The legislation covers both residential and commercial tenants. Under the state government's plan, the restrictions on rent increases and termination of tenancy agreements will be extended until 28 March 2021.

"To ensure that measures aimed at protecting residential tenants are not exploited, we have narrowed the focus of the act so that the prohibition on rental increases only applies if the tenant is experiencing financial hardship as a result of the COVID-19 pandemic," Chapman said.