More than 1 million people have yet to renew their tax credits ahead of the 31 July 2018 deadline, HMRC has warned.
Those who miss the deadline will see their payments stopped, and will have to pay back the tax credits they have received since 6 April 2018.
Last year, 320,000 customers missed the deadline and had their payments stopped or altered as a result.
HMRC is urging those who have not renewed their tax credits for 2018/19 to do so online, through the government website or HMRC app.
Tax credits can also be renewed by phone or by post.
Angela MacDonald, director-general of customer services at HMRC, said:
"We've improved our services so customers can renew their tax credits at a time that's convenient to them but the 31 July deadline is fast approaching.
"I urge customers who have yet to renew their tax credits to do so as soon as possible, to avoid their payments being stopped."
Talk to us for advice on tax credits.