My table has four fields: Total Price, Total Paid, Amount Owed, and Payment Status. When the value of Total Price and Total Paid are the same, the value in the Amount Owed field, predictably, shows "$0" – however when I use the value of {Amount Owned} in a custom formula for the Payment Status field, it shows up as "7.275957614183426e-12" i.e. a near-zero value, but not zero. This is causing my formula to break, although I can work around it by checking if the value is "< 0.01" instead of "== 0".
This appears to be a bug in AirTable,
Total price is a manually entered currency value.
Total Paid is a rollup field, summed from a different table using SUM(values)
Amount Owned is a simple formula subtracting Total Paid from Total Price
And Payment Status is a formula that looks like this:
IF({Total Price} > 0,
IF({Amount Owed} > 0,
IF({Total Paid} > 0,
"Partially Paid",
"Unpaid"),
"Fully Paid"
),
""
)