Millions of motorists are being urged to act now as some MOT extensions are coming to an end.
It comes as tests were halted for months during the coronavirus lockdown.
Around 11.3 million MOTs are due in the next three months and those who miss the deadline will face a £1,000 fine.
And Martin Lewis, 48, has previously urged UK drivers to act quick to avoid a penalty.
Back in March, the DVSA introduced a six-month extension on all MOTs that were due during the outbreak.
Anyone whose car check was due between March 30 and July 30 would have had their deadline extended by six months.
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Now those MOT certificates that were due at the start of lockdown will be approaching the new deadline.
According to motoring chain Kwik Fit, around 11.3 million vehicles are due for their tests between now and December.
MOT tests were made mandatory again in the UK on August 1.
If your MOT was due up to or on July 31, it would be automatically extended by six months.
Roger Griggs, communications director at KwikFit, warns getting appointments at short notice will be a "lot trickier".
He said: "The MOT is a vital safety check, but it is something that many drivers leave to the last minute to sort out and in previous years that has left some car owners driving without an MOT.
"The impact of Covid-19 and the MOT extension will make this problem much worse as finding available MOT appointments at short notice will be a lot trickier over the coming months."
The DVSA has encouraged road users to secure their tests as soon as they can to avoid being caught out by the sudden demand.
Previously, Martin spoke on Good Morning Britain about MOT extensions.
He said: "During the coronavirus pandemic MOT testing was paused.
"If your MOT was due between March 30 and July 31, you automatically received an extra 6 months, eg, July 24 becomes Jan 24, 2021.
"But from August 1, MOT testing will restart – meaning if your MOT's due from then onwards, you'll need to sort the test as usual."