I recently launched a new donation page that allows recurring payments via PayPal Standard. I noticed a couple of recurring contributions had a status of "Pending (Incomplete Transaction)". It turns out both donors had entered "1" in the Installments field. I expect that would either be considered an input error or perhaps it would simply process it like a single payment. I tried it myself and found that the donation page will submit, but PayPal then displays an error:
The link you have used to enter the PayPal system is invalid. Please review the link and try again
I assume the donors simply gave up at that point. I've reached out to both to find out. I suspect they thought the option for a recurring payment was actually a directive, and they entered "1" to ensure they were making a one-time donation.
Is there an option to force the Installments field to accept only values greater than 1?
While I was at it, I decided to try entering a zero in the Installments field. This makes no sense, but you never know what people will try. It actually processed the transaction with a payment. When I look at the transaction on "Find Contributions", it shows it as "Installments: (ongoing)". When I follow the link that is provided in the receipt to update the recurring contribution, it shows "Number of Installments 0".