Taxpayers' last-minute rush to file returns for the assessment year 2013-14 has made the website of the income tax department run slow, ahead of the soon-to-be-concluded July 31 deadline.

More taxpayers are filing their returns online as the central board of direct taxes (CBDT) has made e-filing of the returns mandatory for even people who have an annual income of up to Rs 5 lakh.

Some problems in accessing the website for e-filing returns are primarily because of network restrains of the local Internet service providers (ISPs).

Problems in filing returns due to slow website prompted many to demand the revenue department to announce an extension in the deadline. When contacted, an assessee said, "The department must extend the deadline by at least 15 days to allow assessees to file their returns."

The finance ministry said in a statement that it e-filing of returns reached record peak of more than 85,000 per hour on July 30.

Till Monday, more than 82 lakh taxpayers had e-filed their income tax returns for the assessment year 2013-14, which represents an increase of 40 per cent from the corresponding period of last year.