It makes no difference.

I figure if I cut them before I chit them, they'll have a chance to 'heal' over the cut surface. But probably doesn't really matter.

I don't do anything when planting potatoes, just cut, drop in the trench, and cover with soil. I've never had a problem even in my heavy soil. I do live where it almost never rains, so I can control the moisture level of the soil. Not sure about those in wetter climates.

Potato seeds will rot anyway, Only a small portion near the eye
is needed to make the seed to sprout and grow. Plus, when you plant them it is cold and roting is not a problem.

I tried chitting seed potatoes indoors last year. I think because it is very dry in my house, a number of the cut pieces were dehydrating more than sprouting. Next time I buy seed potatoes, I'll aim for smaller potatoes rather than cutting the larger ones.

Perhaps cutting after chitting would work better in a very dry house than cutting first.

The method I use has never failed me (many, many years): cut, dip cut surface in powdered (micronized) sulfur, place in a well lit room (not in direct sun) at appx. 70 deg for about a week, plant. If your seed pieces are in good shape you can't go wrong, if they are dried and shriveled when you cut them you are asking for failure.

You can put them in frig, after cutting, for a while.

When they are chitting/greening in single layer, there is no reason
for them to rot. Once planted, they will eventually rot/ferment.

This is very interesting to me. In the US cutting up seed potatoes seems to be standard practice. In the UK we are warned strongly not to do it, not to save our own seed potatoes from year to year and only to buy certified disease free seed potatoes. I don't think it is entirely a marketing ploy. The possibility of potato disease is something the authorities are constantly reiterating. I wonder why practices are so diffent in the US?

yes flora i never cut my potatoes up when i lived in uk my 2nd season growing in usa so might try a few see what happens

Flora: maybe the soils in the UK largely have endemic disease populations which cause cut seed pieces to rot. My plots never have solanaceous crops more than 1 year in a row and never more than 1 in 4 years. Just a thought. Commercially grown potatoes are almost all cut seed pieces. Buying CERTIFIED disease-free stock is definitely a good idea. In the US there are several levels of certification which basically are levels of guarantee that they really are disease-free. I used to now much more about certification but have forgotten.

Flora, you're talking about two different issues. Most of us in the US do not keep our potatoes from last year to grow this year. As in the UK, we will have disease problems unless we use disease-free seed potatoes. We do, however, cut our (certified disease-free) seed potatoes into pieces to get more plants and space them out appropriately. I seriously doubt that would be a problem in your part of the world. But, of course, I could be wrong.

This is a related topic I need to resolve. Some of my seed potatoes were purchased earlier than I usually do. They have been sitting in my cellar covered with burlap. I guess 55-60 degrees F must be too warm, because they have long white sprouts on them now. I was planning to chit them soon. My question is should I just knock the weak sprouts off and let stronger chits grow or what? I think this plan will work because in the past I received fingering seed from SSE that had shriveled up shoots. I don't recall if they chitted in open air, but they grew spuds... Any thoughts?

Barth, If those white pale sprouts are short, less than 1/2", leave them on and start the process of chitting/greening.
Once they get light they will get greenish. but if they are too lanky, just brake them off. New ones will grow.

ABOUT, TO CUT OR NOT TO CUT.

Aside from soil issue, cutting serves purposes:
You don't want to waste.You just need one or two eyes per seed. Instead of planting one big seed(w/too many eyes), you cut it into pieces an plan them few inches apart. This way the stem will grow apart an thereby will have more room for hilling and tuberss.

arent all potatoes seed potatoes? I thought, because the ones that sit in my fridge too long develop eyes. Do I have to buy special seed potatoes or can I just get what I want to grow from the grocery store?

Flora, from the UK also, only 2 years in the US, my Pop always cut and chitted, and My hubby did a PHD sponsored by the British Potato Board before it was disbanded, and he cultured his Potatoes by using a apple corer for each eye! and had great results apparently! he get's cross at me, as I use my Pop's wisdom, 3 eyes at least but cut each pot no more than 3 times! we are not foogies, well we are getting! on, I was 40, 3 weeks ago and hubby 43, Pop's was born 1906!(er dead now...sorry! Passed on!) so maybe?
but chitting is common in the UK, AND! and! you are always the first to take the piss about the American Paranoia, which I have to say I agree with, but! seed pots! My Pop always held on to a few of his best from year to year, unless they got diseased, to replant, then he would get certified pots, he couldn't afford to buy every year.
PS Flora can you get some fish and chips for me, eat them and tell me how lush they are..I really want fish and chips!
WARNING, don't tell me you can get them here, they are not fish and chips, fish is fine passable but the chips YUK!