l did/made a big mistake.

[Tan Elaine]

l did/made a big mistake.

Can either word be used? Thanks.

 

[Rover_KE]

No. 'I made a big mistake.'

 

[MikeNewYork]

In some contexts, you can use "I did make a big mistake".

 

[emsr2d2]

Mike's version uses emphasis which would be appropriate in some contexts, but the grammatical rule you need to remember is that it's "to make a mistake", not "to do a mistake".