Banks, most anyway, post interest at the end of the month. If you set up a scheduled transaction for the last day of the month and use the program during the day, it tries to create the transaction before you know the interest amount. If you schedule for the 1st of the month, you have change the posting date each time. You should allow the transaction to be created the day after and automatically back dated to the last day of the month. Basically, you allow create in advance, why not create in "arrears".
Gyle McCollam commented
My accounts post at all different times. However, I have found that you can have the system automatically generate a posting of the interest received or charged (credit card or loans) from the reconciliation of that account. However, it would be helpful if the system could remind you without posting a transaction on the date that the amount occurs.
Robin Favron commented
I'm only a day old with GC, coming from Quicken and still having a hard time just entering a scheduled transaction but I'll take a guess that it might help to turn off Create automatically and use Remind in advance 0 days instead. This is because in Quicken you can edit a transaction before entering it into the register, but that's because Quicken lets you enter a scheduled transaction into the register manually any time you want, which I haven't seen here yet.