Short answer: To prepare for a smart contract audit, freeze the code at a tagged commit, define exactly which files are in scope, document the design, roles, and invariants, get test coverage high and passing, fix everything that free automated tools find, and plan time for a fix review afterwards. Auditors bill for time, so every hour they spend on setup, missing context, or obvious bugs is an hour not spent finding the issues that matter.
Audit cost scales with how long reviewers need. Code that compiles cleanly, explains itself, and has already been through automated checks lets reviewers go straight to business logic, economic attacks, and cross-contract interactions, which is where serious vulnerabilities tend to hide. Firms such as OpenZeppelin start every engagement with a preparation stage for exactly this reason. For price ranges, see smart contract audit cost.
Pick a commit, tag it, and stop changing it. Code that moves during a review costs more and gets a weaker review. If you must change something, agree with the auditor how it will be handled.
List every in-scope file and its line count, and every file that is out of scope, such as unmodified forks of audited libraries. Name the chains, compiler version, and any external protocols you integrate with.
Reviewers should be able to clone, install, compile, and run tests with documented commands. Pin dependency and compiler versions.
Explain what the system is supposed to do: architecture, user flows, and how funds move. A diagram of contracts and their calls saves reviewers hours.
List every privileged role (owner, admin, minter, pauser, upgrader), what it can do, and who will hold it in production: a multisig, timelock, or governance contract. State what you assume about oracles, bridges, and external tokens.
Write down the properties that must always hold: total shares never exceed total assets, users can always withdraw their own balance, and so on. Invariants guide the review and can be turned into fuzz tests.
Aim for high, passing coverage of the in-scope code, including failure paths. Add Foundry invariant tests or Echidna properties for the invariants above.
Run Slither and Aderyn locally or in CI (see security checks in GitHub Actions), and run a free smart contract scan on the repository. Fix or document every finding, so reviewers don't spend paid time on issues a tool already caught.
Tell the auditor what you already know is risky or unfinished, and where you most want their attention. Known issues listed upfront are not re-reported as findings, and focus areas get more depth.
Reserve engineering time right after the report to fix findings, and book the auditor's fix review in advance. Sherlock notes that almost every protocol needs at least one remediation pass.
Fix the findings, get the fixes reviewed, and make sure the deployed bytecode matches the audited and fixed commit. Any later code change is unaudited until it is reviewed. Continuing to run automated scans on new commits catches regressions between audits. For launch steps beyond the audit, see the DeFi pre-launch security checklist.
Q: How do I prepare for a smart contract audit?
A: Freeze the code at a tagged commit, define the scope, document the design, roles, and invariants, raise test coverage, fix what automated tools find, list known issues, and book time for the fix review.
Q: How far in advance should I book an audit?
A: Well-known firms are often booked weeks ahead, so contact them as soon as the scope is stable. Use the waiting time to work through this checklist.
Q: Should I run automated tools before an audit?
A: Yes. Slither, Aderyn, and an AI scan catch many common issues in minutes. Fixing them first means reviewers spend their time on logic and economic risks, which usually lowers cost and improves results.
Q: What happens if I change code during the audit?
A: Reviewers may need to re-read changed areas, which adds cost, and changes made late can go unreviewed. Agree with the auditor how changes are handled before the review starts.
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Run Free Scan →Smart contract audits cost roughly $5,000 to $250,000+ in 2026, with most DeFi audits between $25,000 and $100,000. Prices by contract type, what drives cost, timelines, and cheaper ways to prepare.
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