Run the two systems side by side by naming one of them the record of truth, feeding the same real work into both, comparing a short list of outputs every day, and switching only when exit criteria you wrote down in advance have been met. Until then the old system stays on and stays in charge.
Name the record of truth
For a vacation rental manager the test is simple: if the two calendars disagree, which one does the team believe. During a parallel run the answer is the old system. It keeps taking bookings, it keeps feeding the channel manager, and guests and owners are dealt with from it.
The new system is shadowing. It receives the same bookings and produces its own calendar, cleaning schedule and owner figures, and nobody acts on those until the switch.
Only one system should ever push availability to your listing channels. Two systems both writing to the channels is how double bookings happen.
Limit the double entry
Entering everything twice is the real cost of a parallel run. If it drags on, staff stop doing it and the comparison becomes worthless. Ways to keep it small:
- Feed bookings into the new system automatically from the same source the old one uses, so only exceptions are typed twice.
- Run a subset first. A handful of properties, or one owner's portfolio, will surface a lot of the problems.
- Give the double entry to one named person, not the whole team.
- Set an end date for the run, and extend it deliberately if needed, never by drift.
- Skip double entry for anything you can check afterwards from a report.
What to compare each day
- Bookings: same count, same dates, same property, same guest.
- Blocked dates and owner stays.
- Nightly rates and totals, including cleaning fees and taxes, on each new booking.
- The cleaning and turnover schedule for the next few days.
- Payments received and balances due.
- Messages that should have gone to guests, such as check-in instructions. Keep the new system's guest messaging switched off or pointed at a test address so nobody gets two.
At month end add the owner statements. Statements are where small rounding and fee differences show up, and owners notice them.
Write the exit criteria first
Decide before the run starts what passing looks like, because once people are tired of double entry everything starts to look good enough. For example: a set number of consecutive days with no unexplained differences, one full month end with owner statements matching, every member of staff having done their own job in the new system at least once, and every difference found so far either fixed or understood.
Write it down and have whoever runs operations sign it off, not the person who built the system.
Keep a way back
After the switch, keep the old system readable for a while and keep an export of it. Know the steps to return: which system pushes to the channels, how bookings taken since the switch get back into the old one, and who makes the call.
Check the old contract's renewal date too, so the parallel period does not roll you into another year by accident. Our software bill calculator, a free calculator, shows what the old bill comes to over a year, which puts a price on each month of delay.
This is how we run every switch at Hiro. The new system works beside the old one on real bookings, and nothing is switched off until the customer has watched it hold up. Channel connections stay as they are. Our guide to owning your software has a longer section on switching risk, and there is a page on what vacation rental managers rent and can rebuild.