The deadline to switch to the unit area system of property tax calculation for residents of the Calcutta Municipal Corporation area has been extended by 10 months, till March 31 next year, officials said.

The corporation is simplifying the self-assessment form a taxpayer has to fill in to switch to the unit area tax regime.

The new form will be ready in another couple of months, after which the CMC is likely to launch a drive to persuade people to shift to the unit area system.

The new system promises to make calculation of property tax more rational. Under the unit area system, the tax of a property will depend on its age and location, whether it is on a kuccha or a pucca road, and whether it is self-occupied or rented out.

Civic officials said the unit area system would reduce the property tax burden of those who are unnecessarily paying a high tax. Those who are unjustly paying a low tax will have to cough up more.

“We have extended the deadline till March 31, 2020. The earlier deadline was May 31, 2018. We want to give more time to the people to understand the new system,” said deputy mayor Atin Ghosh, who also heads the CMC’s assessment department.

The unit area assessment method replaces the annual rental value system, in which the property tax was calculated on the assumed rental value of a property.

“In the old system, we used to calculate the amount a property could fetch as rent. The valuation of the property was based on the assumed rent. The tax was a percentage of the annual valuation,” a CMC official said.

In the unit area system, a base value is fixed based on location. “The base value for Mukundapur will not be the same as that of Alipore,” the official said.

About 1 lakh property tax payers, out of around 8 lakh, have switched to the unit area assessment system.

The self-assessment form is available on the CMC website and also at the e-Kolkata citizen service centres of the civic body.

“The form has a detailed description of how to fill it. If someone still fails to understand a point or two, he or she can visit the CMC headquarters on SN Banerjee Road, where a helpdesk has been set up,” the official said.