Pending payments Query

[Thanos]

I have built a property management app with a property table, payment table.

property table has
Unit Number, Name, Phone and Email, rent etc
Payment table has
unit number, payment amount, payment type, month and year.
I linked both the table to unit number
I group all payments which are posted by year and month.

Now, I am working on finding the missing payment report for every month. I tried all options in appsheet. But i could not find a cross-reference query to generate a pending payments report.

Any helps is highly appreciated.