Predict monthly expenses: most of next month is already decided

Take a renting household with ₹1,18,000 of take-home pay credited on the 1st, a personal loan, a car loan, a child in school and one credit card cleared in full each month. The figures are illustrative; the method works on any year of statements.

Class A is fixed in amount and date: ten identical debits a month. Rent of ₹21,000. The ₹9,964 EMI on a ₹3 lakh personal loan over 36 months at an illustrative 12 percent. The ₹11,551 EMI on a ₹5.5 lakh car loan over 60 months at an illustrative 9.5 percent. A ₹6,000 SIP, ₹4,000 to the house help, ₹5,000 to parents, a ₹1,180 monthly term premium and three small AutoPay mandates. Together ₹60,292, 51.1 percent of take-home. This is the fixed expenses list, the one part of a monthly expense forecast that can be exactly right.

Class B is fixed in date but not amount: electricity, piped gas and the card bill. Class C is fixed in amount but not in month: the quarterly school fee, annual premiums, a yearly renewal. Class D is everything that genuinely varies, paid by UPI, debit card or cash. Card swipes are not in D. They arrive a month later inside the card bill in class B, and counting them in both places counts them twice.

For a bill that arrives on a fixed date in a varying amount, take the last three, average them, and note the highest. The card bill here was ₹13,900, ₹15,600 and ₹14,500 from July to September: an average of ₹14,667 and a maximum of ₹15,600. Piped gas averages ₹700 and has not gone above ₹710.

The card bill has a property the others lack: it becomes known before it is due. This card's statement closes on the 25th and is due on the 15th of the next month, so October's bill, ₹14,380, has been printed since 25 September. The three-month average was off by ₹287, 2.0 percent. Once the statement closes, stop forecasting that bill and move it to the exact column.

Electricity is where a three-month average fails, because the window can sit in the wrong season. Averaging January to March 2026 gives ₹1,543. April's bill was ₹2,870, so the average came up ₹1,327 short, 46.2 percent of the real bill. May's ₹3,420 was 167.2 percent above January's ₹1,280, and April to June carried 37.9 percent of the year's ₹24,400 of electricity. For a seasonal bill, use the same month last year from your twelve-month window, and keep the recent maximum as the high end.

Pull every debit from twelve months of statements that did not repeat monthly but will repeat: fees, premiums, renewals, the festival bonus. Put each in the month it last fell, at the amount last paid. That is class C, and it is exact in the same way class A is, as long as the price has not changed.

This household has eight. The ₹18,500 quarterly school fee in October, January, April and July. ₹14,000 of annual school charges in June. A ₹28,600 family health premium in March. ₹13,900 of car insurance in August. A ₹9,600 gym membership in May. A ₹1,499 annual streaming plan and a ₹4,000 festival bonus in November. A card annual fee of ₹2,000 plus 18 percent GST, ₹2,360, in January. The year's total is ₹1,47,959, an average of ₹12,330 a month, but nine months carry some of it and three carry none.

Here is class C beside the rest of the forecast for the next twelve months.

Class D is what leaves by UPI, debit card and cash, whether the app is GPay, PhonePe or Paytm. Total it for each of the last six months. Here, April to September: ₹16,900, ₹19,700, ₹15,600, ₹17,300, ₹18,800 and ₹16,400. The mean is ₹17,450, the low ₹15,600 and the high ₹19,700: a range of ₹4,100, with the top ₹2,250 above the mean and the bottom ₹1,850 below it. On an average month the actual lands ₹1,200 from the mean, 6.9 percent.

Six months is deliberate: three is too few to show the range, and twelve drags last year's festival month in at the wrong place. October 2025 was Diwali month, on 20 October, and class D ran to ₹21,900, ₹4,450 or 25.5 percent above the six-month mean. Diwali 2026 falls on 8 November. Last October is a poor guide to this one: the festival spending moves to November, alongside the ₹4,000 bonus already on the calendar.

The usual shortcut assumes next month looks like last month. Below is that shortcut against the four-class method for each month from April to September 2026, each forecast made only from the statements available at the time: class A exact, class B from the prior three months' average of each bill, class C from the calendar at last year's amounts, and class D from the prior six months' mean.

With salary on the 1st, the account is lowest on the last day of the month, just before the next credit. October's central forecast is ₹1,13,162 against ₹1,18,000 of take-home, 95.9 percent; the high case is ₹1,15,662, 98.0 percent. Starting October with ₹6,000 in the account, the balance on 31 October is forecast at ₹10,838, or ₹8,338 with every range at its top. The month fits.

It fits unevenly. By the 15th, after class A, the school fee on the 10th and the card bill on the 15th, ₹1,01,616 has left, 89.8 percent of the month's forecast outflow. The second half of October runs on class D and little else. Whether each debit clears on its morning is a question of dates against payday, worked day by day on the never-miss-a-bill page.

The buffer comes from the uncertain classes. In any month after October the high case sits ₹3,183 above the central one: class D at its six-month high and the card bill at its three-month high. March has a central shortfall of ₹5,669 and a high-case shortfall of ₹8,852. That is the buffer this household needs, and it needs it in one month of the year.

Three things change classes A and C, and each leaves a trace.

A new mandate. A ₹649 UPI AutoPay that started last month is ₹7,788 a year, and it belongs in class A from its first debit, not after three. Scan each statement for AutoPay or NACH debits missing from the one before.

A rate change on a floating loan. Take an illustrative ₹32 lakh home loan with 204 months left at 8.50 percent: the EMI is ₹29,705. If the rate resets to 8.75 percent, the lender can raise the EMI to ₹30,192, ₹487 more a month, or hold the EMI and extend the loan by 7.9 months. The second leaves your monthly forecast untouched and adds about ₹2,34,318 of payments at the far end; the first costs ₹99,206 more over the same 204 months. A reset letter saying the EMI is unchanged is still a change: read the revised tenure.

A premium hike. The health premium rose 7.9 percent at its last renewal and the car insurance 8.6 percent. A renewal notice usually arrives before the debit, and that notice is the moment to update class C.

The work on this page is sorting a year of debits into four classes and pricing each. Unyfy does the sorting from your own transactions. On Pro, its Fixed Expenses screen predicts what the coming month is already committed to: the EMIs, SIPs, rent, premiums, bills, subscriptions and card bill it has seen leave your accounts, so the exact part of the forecast arrives filled in rather than rebuilt from memory. Its Subscriptions list shows each recurring subscription with its amount and whether it is due or paid this month.

What you see is next month's committed outflow as a list, each item named from the lender, insurer or merchant on the debit, with its amount, and what has been paid and what is left so far this month. It is built from bank and card transaction emails and, on Android, transactional SMS, with no manual entry. It never asks for your bank password or UPI PIN, and every payment is one you authorise.

Install Unyfy on Android, or use the web app at app.unyfy.co.in on an iPhone.