Declipper.... :(

I have recently gotten some gigs mixing other's recorded work. I enjoy it a lot!

But people obviously don't often record themselves very well.

I have a new client who has some clipping issues. Since I haven't had to read or deal with this in years, what is everyone using to deal with nasty digital distortion if it comes do to it.
(re-recording isn't possible for this one).

  Alright... well if it is in perfect time and there are repeating parts and one section of a part doesn't have the clipping you can slice and dice the sections to replace the bad ones... or you can zoom into the wave really far and cut out the clip (if you can't turn it down so it isn't noticeable) then blend in a part from elsewehere that is the same note, hit, etc... for drums you can use audio snap and just replace it all with MIDI drums or sample the good hits as one shots and toss them in where necessary... if it's vox and there aren't any repeating parts well that's a drag but you could try using effects and creative engineering to make the clipping sound intentional.

IDK... digital clipping is bad and I don't think there are any real plug in solutions but if it is slight then maybe some zooming in and putting in some precise volume automation you could get rid of some. I'd imagine compressor and EQ notch filtering might help.

Just things I would look at. Cheers.

Oh and R-Mix seems to do some pretty impressive stuff. Wait for the clip and see what lights up then automate that section out. It also some cool filters that might get rid of less intense but consistent clipping

Generally, clipping is hard to fix...

If say chorus one clips but chorus 2, which is a perfect match doesn't,  a copy paste will fix it.  

Other than that.... IDK... I will record it again. Working for others that may not be possible.

That would be one of the problems in working with people who do not know what they are doing. I would contact them, tell them what the problem is and ask for a new track at lower levels. 

Once you clip.... the data that is missing can not be invented to fix it. You can always raise a low level without issues..... but not so easy the other way around. 

Maybe some of the tools mentioned above will get you there in a reasonable way... but IMHO.... the best way is a new track that is recorded better.