My biggest 1040 received 67 K-1s that weren't final last year (so I might have had 70-75 K-1 entries). As far as I know:
- there is no technical limitation, either Lacerte or e-file, that is based on number of K-1s
- the more small-dollar K-1s you have, the more of what I call "-1 errors" will occur - the calculated allowable amount of some deduction will end up being a dollar, and Lacerte will say "-1 is the same as zero; I'm going to produce a detail schedule that doesn't foot" or "-1 is the same as zero; I'm not going to carry that amount to the appropriate place." Combining entries (so all the passive Sch E p 2 loss items get entered as one amount in the Box 1 input, for instance) is a good workaround.
- The more entries of any kind you have, the longer it will take to calculate the return, and the greater the chance that Lacerte will get tired and stop actually calculating, even though it appears to be. The solution to that is to close Lacerte and restart it.
Every year, Lacerte has gotten better and better at handling bigger returns. I would personally not turn down a 200 K-1 1040 return due to software concerns. My quality control system compares expected output to Lacerte output; if yours compares inputs, 200 K-1s is too many to assume that if input looks good that you'll get the expected output.
For entity returns, if you have good workpapers that produce an accurate trial balance, "number of K-1s" limitations are unlikely to be an issue. Entities that receive K-1s have much less robust data entry screens in Lacerte, so you should not anticipate being able to plunk K-1 numbers in and have a complete and accurate return fall out.
In my experience, returns with a lot of K-1s tend to have oddball items where the preparer needs to apply plenty of professional judgement, but that's not a software issue.
