How to Track Contingency in a Custom Home Budget

Short answer: To track contingency on a custom home, give it its own budget line and cost code, never spend from it directly, and move money out of it into the cost code that needed it, with a written note and approval for each move. Each month, report the original contingency, each transfer, and the amount left for every house.

What contingency is, and what it is not

Contingency is money in a house budget for costs you cannot name yet: rock in the excavation, a price increase between estimate and order, a detail the plans missed. It is different from two things builders often mix it up with:

An allowance is for an item the client will pick later, such as tile or lighting. See allowance tracking.
A change order changes the scope or the contract price. See change order tracking.

Who controls contingency depends on the contract. On a fixed-price home it is usually the builder's own cushion inside the price. On cost-plus or guaranteed maximum price (GMP) work, the contract decides. The AIA A102-2017 cost-plus-with-GMP form, for example, has contingency shown as its own line in the schedule of values and requires supporting documentation when contingency is moved to another line. Many residential contracts use their own wording, so follow yours.

Set it up before the first bill

Give contingency its own line in the estimate and budget for each house, with its own cost code. Buildertrend's own help center recommends a dedicated Contingency cost code.
Pick the amount on purpose. Buildertrend's contingency guide suggests 5 to 10% of the project budget as typical. Your number should depend on how complete the plans are, the site, and what your past houses actually needed.
Write down who can approve using it, and whether the client has to sign off. On cost-plus work, the client usually sees it.
If the construction loan budget has its own contingency line, ask the lender early how they want it drawn and what backup they need.

Never code a bill to contingency

This is the most common mistake. When the excavator bills for rock, the bill goes to the excavation cost code on that house, not to contingency. Then you move budget from the contingency line to excavation to cover it.

If bills land in contingency, you lose the one thing the report is for: seeing which trades ran over and why. You also cannot learn from it when you price the next house.

Keep a contingency log for every house

One row per transfer. These columns are enough:

Date
Cost code the money moved to
Amount
Reason, in one plain sentence
Who approved it, and whether the client signed off when the contract requires it
Contingency left after the move

The log is what makes the budget believable. A transfer with no reason or no approval is a question to answer before the month closes.

A worked example (SAMPLE, made-up numbers)

A house budget carries a $40,000 contingency line. In month 3, rock in the excavation adds $9,500 over the excavation budget. The bill is coded to excavation, and $9,500 moves from contingency to excavation with a note. In month 5, the framing lumber package comes in $6,000 over the framing budget. The bill is coded to framing, and another $6,000 moves.

After framing, $24,500 of contingency is left. If the house is not yet dried in and more than a third of the contingency is already gone, that is an early warning about margin, and it is much cheaper to see it now than at closing.

How the software helps

Buildertrend: its help center says to create a Contingency cost code, add a contingency line to the Estimate, and use a negative change order on that cost code when you draw from it. Once approved, the Revised Cost column and Job Running Total update.
QuickBooks Online: bills still have to be coded to the real house and cost code. If you report budget versus actual from the books, keep a revised budget that reflects every contingency move, or the report will show some lines over budget and contingency untouched.

See Buildertrend and QuickBooks Online for how the two fit together.

What to look at each month

Original contingency for each house
Transfers this month and to date, with reasons
Contingency left, in dollars
Contingency used compared with how far along the house is
Any transfer that is large or has no approval

On a WIP schedule, estimated total cost should reflect what you now expect to spend, so remaining contingency should be reviewed each month rather than assumed to be all used or all saved.

How we handle contingency

Each month our team codes every bill to the right house and cost code, keeps the contingency log current, and shows contingency used and left on each house in your monthly job cost report. Our founder reviews every close before it reaches you. This is part of job costing in Builder Books, $1,500 a month for up to 5 active homes. Builder Controller, $2,900 a month for 6 to 10 active homes, adds a monthly WIP schedule and a 13-week cash forecast. See pricing.

Sources

Common questions

Is contingency the same as an allowance?

No. An allowance is for an item the client picks later. Contingency covers costs nobody can name yet. Track them on separate lines.

Should I code bills to the contingency cost code?

No. Code each bill to the cost code where the work happened, then move budget from contingency to that line and log why.

What happens to unused contingency?

On a fixed-price home it usually stays in the builder's margin. On cost-plus or GMP work, the contract decides whether savings go back to the client or are shared. Ask your attorney if the wording is unclear.

How much contingency should a custom home have?

There is no single right number. Buildertrend's guide suggests 5 to 10% of the project budget as typical. Base yours on plan completeness, site risk and your own past houses.

By John Mos, Founder. Updated October 26, 2026. We do not give tax or legal advice. Please ask your CPA or attorney.

How to track contingency in a custom home budget