British Gas, EDF Energy and other energy companies’ online services have stopped working properly on the final day for customers to submit meter readings.

Websites said they were unable to accept meter readings through their websites or apps, as a result of technical problems. Pages on the British Gas website loaded but it would refuse to accept readings, while EDF’s website said it was down for “essential maintenance work” and that it would be “up and running again soon”.

Other energy companies seemed to be suffering similar problems. Shell Energy’s website was down completely, and customers reported problems with Scottish Power’s online services.

Customers in the UK have been advised by experts including Martin Lewis to ensure that their usage is correctly logged by the end of March, to ensure that they are not hit by unfair charges.

Price changes go into effect on 1 April, and so any usage before that date that isn’t logged with energy companies may be charged at the new – and much higher – rate.

MP Tom Tugendhat was one of many to voice frustration with the outage and its timing.

British Gas encouraged customers to use a form on its website to send in meter readings, which appeared to be working when the systems in its app were not.

Mr Lewis told customers not to worry about any delays in submitting readings – but to do it as soon as they could.

“If you can’t get to do a meter reading today, do it tomorrow, or Sunday, or monday,” he wrote on Twitter. “The nearer to today you do it the less chance of mis-estimates, so don’t panic about missing it (either through your own or the firm’s issue) just get it in as soon as you can.”

Customers were also advised to take photographs of their meters in case of any disputes.