I have an LLP with 4 partners. They have a regular 401k plan. Their deductions for their contributions flow on to the same line of their individual tax return regardless of whether they are classified as a deferral or a match. They send in contributions monthly and try to split the money between deferrals and match on the recordkeeping system ( knowing that this is purely an estimate since they don't really know their pension income ).
What is the administrator supposed to do with this data after year end ? Does he reclassify deferrrals and match for the partners somehow ? It would be better for ADP testing to show as little deferral as possible. Should his software make this computation after the partner net/net pension income is computed? Shoul they then go into the recordkeeper and reclassify these moneys between deferral and match ?
Thank you.

They need "elections" with a percentage just like all of the other employees -- although they have until the end of the year to make them -- because compensation isn't considered earned before then.

Then you need to know what self-employment compensation is for the year -- and you apply the percentage to the self-employment income.

Then you apply the plan's match rate to that contribution.