Most vendor choices can be undone in a weekend. Two or three cannot, and firms usually cannot tell them apart in advance.
Not price, not features. Whether the system holds data you will need later, and whether other systems depend on it.
A tool that does one job and exports cleanly is reversible. A tool that becomes the record for something is not.
Your custodian, because every process touches it. Your performance reporting, because the history lives there and rebuilding it is frequently impossible. Your CRM, because it accumulates the record of every client interaction.
Everything else is usually a weekend and some annoyance.
What happens to my data when I leave. Specifically: in what format, how complete, how long it takes, and whether history comes with it.
Ask before signing. The answer given during a sales process and the answer given during a cancellation are different answers, and only the first one is available to you now.
Ask how you get out before you decide how to get in. The exit terms tell you more about the vendor than the demonstration does.
"Integrates with" covers everything from a genuine live data connection to a manual file export. Ask what specifically syncs, in which direction, how often, and what happens when it fails.
Not choosing the wrong system. It is choosing several systems that each solve a problem and together create the seams where data disagrees.
Every seam is a reconciliation someone has to perform forever, and that person is usually the founder.
Be slow on the three hard-to-reverse decisions and fast on everything else. Firms usually do the opposite, agonising over small tools and choosing a reporting system in an afternoon.
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