I joined tcs 2022 as c3b with 11yrs exp. Right now I'm 12.5yr exp. When can I expect promotion? Will that be c4?

For C4 you need to have strong business justification and should be doing lot of other stuffs apart from your goal sheet.. It will at least take 4 to 5 years to atleast get consider for it.

It looks you are boom period joiner and got good hike while joining.. Im sure they must have given you higher package hence you are in C3b with just 11 years experience.. Seen this trend in post pandemic joiners is even though they have joined with very good hike but they are not satisfied and expecting high numbers in appraisal and promotions.. Due to false hope that once tcs has given they will keep them giving thay.. But that's not how tcs works.. So better to spend some time if you want long career in TCS or else go to market if money is the only criteria

After 5 years maybe :) C4 is not an easy promotion

They will expect you to involve a lot of internal activities. Or get involved in RFP that gets the account a good project.

Before expecting a promotion, ask yourself why do you think they should give promotion to you.