Real Time Information (RTI), will come into force on 6th April, at which point all firms that employ staff, regardless of numbers, need to have new payroll software installed.
While HMRC has promised an easy ride for firms that do make mistakes using the new system, and has even made a last minute temporary change allowing some concessions for certain small businesses that pay staff weekly, the Forum has said firms who've taken no steps at all to be ready for RTI could well find themselves in "hot water" with the Inland Revenue.
In a poll carried out by The FPB last week it showed 18% of employers are still classifying themselves as "not prepared". The study also revealed 60% were ready, with the remaining 21% saying RTI was not relevant to them i.e. they employed no staff.
"It's quite clear that there are businesses out there still not ready even at this late stage. The message we would like to get out there now, even at this point, is that it's still not too late to get on board for RTI - the ship has not sailed," said the group's head of policy, Alex Jackman.
"We know it can seem a daunting prospect to small firms, but it's just not an option to do nothing. Better to act now than have a phone call from an unhappy tax man after 6th April, and that could happen."
Rachel Andrews a financial specialist at the FPB said: "If I had any last minute advice for businesses it would be to have everything you need ready to go. So employee addresses, date of birth, and the correct NI number. The date of birth is more important now than previously, it has to be correct.
"And the correct NI number is also crucial. If any business is unsure to the number's authenticity, they need to submit an NI validation check with HMRC, and they will come back to you," she said.
Mark Paraskeva, CEO SME Division, IRIS Software Group, said: "If organisations have undertaken training to educate themselves on the legislation, ensured they have RTI compliant software in place and have properly cleansed their data prior to the transition date, RTI should not be a cause for concern."