More than 10,000 buy-to-let landlords have disclosed previously undeclared income following a campaign by HM Revenue & Customs (HMRC).
HMRC's Let Property Campaign, which launched in September 2013, has bought in more than £50 million.
The campaign encourages residential landlords to get their tax affairs in order voluntarily.
Caroline Addison, head of campaigns at HMRC, said that 20 campaigns run by HMRC have now together generated more than £1bn across a variety of sectors.
She said: "We want to help educate landlords, so the Twitter evening will give people a chance to get their questions answered by a group of expert organisations."
HMRC will also run a Twitter question and answer evening from 6pm to 9pm on Tuesday October 20 in partnership with several landlord bodies.
It will be answering questions on current tax law for landlords at @HMRCcustomers between 6pm and 7pm and the whole evening can be followed using the hashtag £UKlandlords.
It comes ahead of a tough new tax laws that make buy-to-let less profitable for landlords from 2017 and could inflict unintended damage on the sector, according to mortgage industry experts.