What happens to unused production?

[SMK-at-work]

Say if a city has all it's slots set to 0, even though it's turning out 5 or 10,000 points/turn?

Does it accumulate or is it lost? If it accumulates can it be spent all at once?

[seille]

it is lost. no accumulation. factories are not working so no production stored.

[tweber]

The only reason not to produce is that you consume more supply.  However, you can produce sftypes and place them in units that are not requesting supplies.  You can then turn the supply on when needed.   So, there is not a good reason not to use all your production. 

[seille]

Reasons not to produce ? Mhh, usually you have always to replace some losses.
But even my armies are filled completely i can produce PP to research or for buying action cards if available.
I usually turn all not really needed production into PP production to get my hands
on the better equipment. I would never "close" any of my factories. Mostly i would like to build some more [:D]
 

[SMK-at-work]

Some cities can be limited so they cannot produce supplies or PP's, so they have to produce SF's, sometimes a very limited subset - eg just a/c or just ships, and the time may not be "right" to make decisions about what it is yuo need in those subsets

[seille]

Mhh, in such a case it would be indeed a option to stop any production, but i never had such a case so far.
There was always something i was able to produce (and what i needed). But you´re right that´s a question
of how the scenario is designed.