Inputs and starting point

The baseline forecast uses a current checking balance, a local reference date, expected income, bills and other obligations, an everyday-spending state, a minimum buffer, and a 30-, 45-, or 60-day horizon. The start and end dates are both included.

Money is converted to integer cents before calculation. Dates are validated as calendar dates in YYYY-MM-DD form without implicit timezone conversion. The engine does not read a bank account, infer missing transactions, or move items for weekends or holidays.

Balance freshness

A recommendation requires a balance confirmed for the forecast’s reference date. A saved plan can retain income and bill schedules, but its balance becomes stale on a later local calendar day. The user must refresh that balance before the result can return to current status.

Activity dated today needs an explicit treatment because the displayed balance may already contain it. An item marked already reflected is excluded from future movement. A still-pending item is included. Unknown same-day activity keeps the result provisional; unknown income is excluded while unknown obligations are treated conservatively as pending.

Income and obligation schedules

Income can be weekly, biweekly, monthly, twice monthly, or irregular and dated. Obligations can be one-time, weekly, biweekly, or monthly. Recurrence advances from an explicit anchor and stops at the inclusive horizon.

Monthly dates that may not exist in every month require an explicit short-month choice. Twice-monthly income uses two configured month-day rules. The engine does not silently change an invalid date. A past one-time obligation remains unresolved until it is marked handled, removed, or moved to a current or future date.

Conservative same-day ordering

Actual institutions can post same-day activity in a different order. When the order is unknown, the baseline calculation uses a conservative sequence to expose a possible within-day low:

  1. pending obligations, in stable source order;
  2. the day’s everyday-spending amount; then
  3. income, in stable source order.

An immediate purchase scenario places the proposed purchase before the other pending outflows on the reference date. The forecast reports both the running low within a day and the balance after all included events for that day.

Everyday spending and incomplete assumptions

Everyday spending has three distinct states:

  • Unknown: no daily event is added, but reviewed spending room is withheld.
  • Confirmed zero: the scenario deliberately assumes no additional everyday spending.
  • Included: a nonnegative daily cent amount is applied on every date in the inclusive horizon.

Unknown is not interpreted as zero. Missing required values, unresolved overdue bills, unknown same-day activity, stale balances, recovered saved data, and an incomplete assumptions review can all prevent a current recommendation even when partial arithmetic is available.

Low point, buffer, and spending room

The starting balance participates as a possible low point. The engine applies each dated event in order and records the first occurrence of the lowest running balance. It also reports the first time the forecast falls below the selected buffer and the first time it falls below zero. Those are separate signals.

A reviewed spending-room value is available only when the balance is fresh and material assumptions are resolved. It represents modeled room above the chosen minimum buffer at the forecast’s tightest point. It is not a guarantee that the bank balance will remain at that level and cannot prevent an overdraft.

Ending balance = starting balance + included inflows − included outflows

Temporary scenarios and export

Purchase tests and other timing scenarios are calculated from a copy of the baseline. They do not mutate the saved plan. An exported workbook represents the baseline forecast rather than silently including temporary scenarios, and it is a snapshot rather than a live bank record.

What the forecast cannot know

The calculator cannot verify the balance, amount, date, pending status, bank posting sequence, holds, fees, payroll changes, unentered spending, or activity outside the selected horizon. It does not predict income or bills. Results are estimates produced from the information and assumptions entered by the user.

Review the real account and scheduled payments before acting. Payday Forecast provides an organizational tool, not financial, legal, tax, credit, or investment advice.