Use the frequency that best describes the full cost. Annual insurance can be entered as Yearly, rates may be Quarterly, and a twice-yearly bill can be entered as 6 Monthly.
The calculator spreads recurring costs into comparable totals, so a $1,200 yearly bill has a $100 monthly effect.
For costs that are truly irregular
Estimate a sensible yearly total, then enter it as Yearly. Repairs, gifts and medical costs often become more honest when you look at a whole year instead of a perfect month.
Worth knowing: “Once” is not treated as an ongoing monthly amount. Use a recurring frequency when the cost should affect the regular budget.