It really depends, it is a trade-off between having reservations that may not happen vs only having guaranteed reservations.

You have a few things you can modify:

If you're super-busy and you don't want to be bothered unless you have a guaranteed reservation then set auto-cancel.  (you can tell your customers this in your provisional notification too)

However, if you want to maximise all feasible business - then be a little more flexible and keep provisional bookings - but follow up with an email or phone call.

Let's look at the flow in this diagram showing the customer flow through making an online booking, and when reservations are created...

Ideally, you want your customers to make confirmed reservations (secured in some way with credit card details or payment)

i.e. the customer flow through the online booking:

  1. leave details / register - provisional reservation
  2. card details / pay - confirmed reservation

But the ideal route doesn't always happen, the question here is how do you want to handle things when they don't go quite to plan.  They might intend to pay, but things can go wrong, for example:

  1. can't find credit card
  2. get interrupted
  3. card not accepted

The point is you have a choice:

  1. EITHER you are only interested in confirmed reservations.  Just ignore others.
    • PROS - your inventory won't be taken by non-payers.  You don't have to chase up provisional bookers to find out what when wrong
    • CONS - you may be missing out on rentals where people were serious but had trouble with credit card...
  2. OR you do still care about provisional bookings:
    • PROS - you maximise the opportunity to take bookings from people online
    • CONS - you have to do work to chase up on provisional.  Inventory might be taken by no-showers until you can confirm.

Once you've made your choice, here is what you do:

  1. only interested in confirmed reservations.  Just ignore others.
  2. OR you do still care about provisional bookings:

you decide, but let us know if you're still having trouble deciding what is best for your business.

See also

Auto Cancel provisional bookings 

online checklist