Horizontal lines at the bottom of iMac(M1,2021) screen

It is a common hardware fault as can be seen from various posts in the Apple Community pages.

I checked with the Apple service provider. The cost of repair is Indian Rupees 50,683 =USD 600 at the current exchange rate (which is around USD 2,100 in Purchasing Power Parity).

My thoughts on this are unprintable.

Thanks for all your help.

FWIW, it's a hardware problem and needs looked at by Apple.

There is no software solution, you will have to contact Apple to get it fixed.

Even I too have same issue I bought iMac 24 inch M1 in 2021, I normally use 2 to 3 days in a week, all of sudden screen started flicking. Apple service Center suggested for screen replacement which cost approximately $900 SGD. I am not sure how apply is selling products now a days with loss of trust on their products.

My guess is your graphics card has tanked, probably through overheating. *Or* your video cable has gone bung. You can’t do anything about the graphics card in an integrated logic board, so it would cost a packet to replace the logic board. If you hook it up to an external monitor do you have the same issue?

Screen replaced free of cost in apple care scheme. Thanks

You won’t find official updates here for this or any other issue. Your only option is to schedule an in-store repair appointment with Apple/Apple-authorized service provider. If their resolution is unacceptable, you can vent your frustration here Feedback - iMac - Apple. Good luck!

If the repair is out of your budget ranger an less costly workaround is to get a 3rd party monitor, put it infant of the iMac and set the iMac's monitor brightness to off and use the 3rd party monitor. 4K monitors can be had for $200 and up for 27" and $300 and for 32": brand LG.

Try safe booting the Mac and see if still occurs

Just for the record, we are just users, and other than offering some hail mary advice can only commiserate with you. If you want Apple to see this send feedback:

Product Feedback - Apple

Exactly the same issue with 24" iMac M1 after 2 years 11 months - only option was replacement of screen at my expense - over £630 - not happy!

After reading all the threads related to this issue, I've contacted Apple chat support and tried to negotiate a free repair for this widespread issue.

Apple chat support said that they don't have the authority to do this and ask me to contact phone support. Phone support said the same thing and asked me to take the iMac and go to Apple store. And Apple Store support said they can't do anything unless the issue appears in this Apple Service Programs list, and he suggested me to leave a message in Apple Feedback.

Everyone, please leave a feedback to make Apple fix the issue.

Also...

Persistent horizontal lines appear on iMa… - Apple Community

Same solution:

Have it fixed, and send feedback.

Product Feedback - Apple

Assuming your purchased AppleCare (always a wise move) then it will be covered. I have been a long time Mac owner and have owned many of them, when I invest that much money in a computer I want the peace of mind that AppleCare offers. If you passed that up and it is a hardware issue then please consider this instance a lesson learned about self insuring. Most of the time it doesn't pay off, until that time you need it.