Paycheck budget: split one check into bills, buffer, and what’s left

A monthly budget answers a question you are not asking. You are not paid monthly. You are paid every other Friday, and between one Friday and the next, certain bills come due. The question that matters is: does this check cover the bills due before the next one, keep checking above the floor, and leave anything over? That is the whole calculator, and it is most of what a paycheck budget is.

What the calculator does

Enter the net amount of this paycheck, what is in checking right now, your payday and the next one (fourteen days later by default), and the floor you keep in checking. Then list your bills with their due dates. The calculator:

1. picks out the bills due on or after this payday and before the next one,
2. subtracts them from the check,
3. tops checking back up to the floor if it is under,
4. shows what is left to route.

The default numbers are an example: an $1,800 check, $420 in checking, a $500 floor, half the rent at $900 four days after payday, a $382 car payment nine days after, and a $95 phone bill fifteen days after. The phone bill falls after the next payday, so it belongs to the next check. This check covers $1,282 of bills, leaving $518. Checking is $80 under the floor, so $80 is set aside, and $438 is left to route. Replace the example with your bills and the answer is yours.

Which bills belong to which check

The rule is simple and worth saying plainly: a bill belongs to the paycheck that is in the account when it is due. A bill due on payday itself belongs to that day's check, since the deposit lands before the debit. A bill due the day before payday belongs to the previous check, and it is exactly the kind of bill that overdraws people, because the money to pay it arrived two weeks ago and has been sitting in checking looking spendable.

If you have a bill that always lands a day or two before payday, the fix is not willpower. It is one phone call to move the due date to a day or two after payday. Most billers will do it. Ample flags these bills as "due before the check that should pay them" and suggests the change.

Two checks, unequal loads

Because bills cluster around the first of the month, the two checks in a month rarely carry the same load. A first-of-the-month check might cover rent, a car payment and insurance; the mid-month check might cover a phone bill and a streaming charge. That is normal. It does not mean the light check is free money.

There are two ways to handle it, and both are fine:

• Let the light check carry the heavy one. Route the light check's surplus to savings, and let the buffer absorb the heavy check's crunch.
• Split the big bill. Rent and mortgage are often payable in halves. Half of each out of every check makes the two loads nearly equal, and, on a mortgage, a third half in a three-paycheck month goes to principal.

Either way, the buffer floor is what makes the uneven pattern safe.

The buffer floor, briefly

The floor is the balance you never plan to spend. It exists to absorb a bill that clears early and a normal week of spending in the gap before the next check. The calculator tops checking up to the floor before it calls anything "left," which is the right order: a buffer you rebuild only after savings is a buffer you never rebuild. If you do not have a floor yet, the checking buffer guide works one out from your largest bill and your weekly spending.

What "left to route" is for

The number at the bottom is not spending money. It is the part of the check that has no job yet, and the best thing to do with it is give it a job the day the check lands, before it blends into the balance. In order of usual priority:

1. Any card balance above 20% APR. Nothing else you can do with $400 returns what paying down a 25% card does.
2. The emergency fund, until it covers a month or two of bills.
3. A named goal, a trip or a repair or a down payment, in its own account.
4. Extra principal on a mortgage or car loan, once the above are handled.

Flexible spending, groceries and gas and eating out, is not in the bill list because it does not have a due date. It comes out of what is left, so if you know roughly what two weeks of it costs, take that off the top before deciding how much to route. The checking buffer guide has a number for a week of it.

When the check does not cover its bills

Sometimes it just does not. The calculator says so plainly, with the shortfall, and nothing about that is shameful; it is a timing problem, and timing problems have timing fixes. Move a bill to the next check if the biller will move the date. Pay a minimum this check and the rest next check where the biller allows partial payments. Draw on the buffer, which is what it is for, and rebuild it out of the next light check. What you are trying to avoid is the shortfall quietly landing on a card at 25%, where a $200 gap becomes a $250 problem.

What Ample does with this

This calculator is a one-check version of the Today screen. Ample knows your paydays from one anchor date, pulls your bills and their due dates from your accounts, assigns each to the check that pays it, keeps the floor, and shows what is left, every payday, with a one-word verdict on how the month is going. When a bill is timed badly against payday, it says so and suggests the date change. When there is money left, it proposes where it should go, and you approve with a tap.