Different groups of people should be set different deadlines for filing their tax returns, to cut the risk of costly errors, MPs have said.
The MPs say e-filing tax returns must be made more attractive
Edward Leigh, chairman of the Commons public accounts committee, said taxpayers were increasingly "going to the wire" in filing their returns.
That meant more errors were made as officials tried to process many returns in a short period of time.
The MPs also say electronic tax filing has risen but more must be done.
Their report shows the Revenue and Customs agency made mistakes in processing almost 500,000 returns in 2004/2005.
People were undercharged for tax by £65m, while others overpaid to the tune of £30m.
And 30,000 taxpayers were given incorrect penalty notices despite filing their returns on time.
Mr Leigh said creating different filing dates for different groups of taxpayers would help spread the load for officials.
"Taxpayers themselves make errors in about a third of tax returns, costing an enormous £2.8bn in lost tax," he said.
"Her Majesty's Revenue and Customs needs to provide clear information on how to avoid the most common mistakes.
"It should improve the training of its call centre staff and the access to specialist advice."
Mr Leigh welcomed early results from electronic returns suggesting a higher take-up of electronic filing, with more than 1.6 million taxpayers filing online or by an electronic service used by their agents.
But the service did not work properly in January 2005 when a large number of people tried to file online, he said.
The committee says the agency has improved the capacity of its e-service but warns it may still not be enough at peak times.
"The proportion of tax returns filed electronically is still low, compared with that in the US and in Australia," said Mr Leigh.
He urged the revenue agency to make e-filing more attractive generally and compulsory for professional tax agents.