Many companies are not yet ready to file their returns under the Goods and Services Tax, GST Network Chairman Navin Kumar told Reuters on Wednesday. He also said that only 18 service providers had received approval to help firms bulk-file invoices online. The window for filing the tax returns opened on August 5, and the deadline is August 20.

But, the system will be stable and can handle the rush, he said. “It will not crash. We are working on the assumption that 50% of the people will come on the last day,” he said, urging companies to not leave it till the last minute.

On August 3, the GST Network had said that of the 71 lakh excise, value added tax and service taxpayers who have migrated to the system, only 44 lakh have finished the registration process.

The GST has brought in a single tax rate to replace India’s complicated tax rules, which include Central excise duty, service tax, additional customs duties, value added tax, entertainment tax and so on. The Centre believes that this will help create a unified market in the country, will help avoid double taxation and increase compliance.