Every deal comes with a 100-day plan. It’s in the IC memo, it’s in the first board pack, and somewhere around day 40 it quietly stops being the plan anyone’s actually working from. 

Nobody talks about this part, because admitting it makes the plan look like theatre. It isn’t, exactly. The 100-day plan does real work. It forces the deal team and the management team to agree on priorities before the deal closes, when everyone still has the discipline to write things down properly. The problem is what happens after close, when the plan meets a business that doesn’t behave the way the data room said it would. 

Here’s what actually happens, in roughly this order. 

Week one or two, you discover something the diligence process didn’t catch. Maybe it’s a customer concentration issue that wasn’t flagged, maybe it’s a key person who’s clearly checked out, maybe it’s a system that’s held together with more duct tape than anyone admitted. This isn’t a failure of diligence, it’s just what diligence looks like from six weeks of data room access versus what you learn from actually running the business. By week four, the plan has quietly reordered itself around whatever that discovery was, and by week eight the original document is mostly a historical artefact you reference in the board pack to look consistent. 

The mistake isn’t that the plan changes. Plans should change when reality disagrees with them. The mistake is not telling the board that’s what happened. I’ve watched operating partners keep presenting the original 100-day slide well past the point it stopped being true, because admitting the plan moved feels like admitting the diligence was wrong. It wasn’t wrong. It was diligence, not omniscience. 

The better move, and it takes some nerve the first time you do it, is to go into the 60-day board update and say plainly: here’s what we thought on day one, here’s what we’ve actually learned, and here’s the plan now. Boards respect this far more than a plan that suspiciously never needs updating. A plan that never changes either means nothing’s actually being learned, or means someone’s managing the narrative instead of the business, and board members who’ve done more than one deal can usually tell the difference. 

If you want a practical habit: rebuild the 100-day plan properly at day 30, not as a full rewrite but as an honest gap analysis between what you assumed and what you now know. Present that gap analysis to the board before they ask for it. It’s the single fastest way to build credibility with a board that’s watched other deal teams quietly bury their original assumptions.