Wash Sale Rule 30 Day Flag Checker
Named inclusive±30calendar-day replacement candidates with independently established substantial-identity flags; no adjusted basis, account aggregation or actual wash-sale determination. Caller independently establishes matching units, evidence, method edition and applicability; output is not compliance, diagnosis, work-safety approval, geological identity or validated hazard prediction.
Description
A replacement acquisition near a loss sale can be flagged for review using calendar dates and independently established substantial identity.
A replacement acquisition near a loss sale can be flagged for review using calendar dates and independently established substantial identity.1
This checker reports candidates within an inclusive thirty-day interval on either side of the sale.
When to use Wash Sale Rule 30 Day Flag Checker
Use this tool when you need to reproduce the stated calculation from measured records or independently selected model inputs. Establish jurisdiction, tax year, applicable authority, and eligible amounts or evidence before entering values.
How to use Wash Sale Rule 30 Day Flag Checker and understand its results
- Establish jurisdiction, tax year, applicable authority, and eligible amounts or evidence before entering values.
- Enter lossSaleDate, replacementAcquisitionDates, callerSubstantiallyIdenticalFlags, following the field table and rules below, then run the tool.
- Read signedReplacementOffsetsDays, namedThirtyDayCandidateIndices. Use the output meanings below to interpret units, signs, flags, and any nested result fields.
- Correct reported input issues and run again. For a successful result, check the stated evidence coverage and assumptions before using it in your review.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| lossSaleDate | Loss sale date | string | Required |
| replacementAcquisitionDates | Replacement acquisition dates | list of string | Required |
| callerSubstantiallyIdenticalFlags | Caller substantially identical flags | list of number | Required |
Enter a real Gregorian loss-sale date and aligned nonempty replacement dates and binary substantial-identity flags. Calculate each signed acquisition-minus-sale offset in days. Retain zero-based indices where the absolute offset is at most thirty and the identity flag is one. Actual loss disallowance and basis adjustments require additional facts.
candidate_i=(|acquisitionDate_i−saleDate|≤30 days) and identical_i Symbols follow the input and output meanings and the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| signedReplacementOffsetsDays | Signed replacement offsets days | list of number |
| namedThirtyDayCandidateIndices | Named thirty day candidate indices | list of number |
{
"input": {
"lossSaleDate": "2026-03-01",
"replacementAcquisitionDates": [
"2026-02-01",
"2026-04-01"
],
"callerSubstantiallyIdenticalFlags": [
1,
1
]
},
"output": {
"signedReplacementOffsetsDays": [
-28,
31
],
"namedThirtyDayCandidateIndices": [
0
]
}
}Limitations and assumptions
Eligibility, rates, dates, definitions, and exceptions are independently supplied facts. The arithmetic is not a complete return calculation or a determination of tax liability.
Missing required fields, unknown fields, wrong types, and violated calculation rules are input issues. Numeric values must be finite; nonfinite results are rejected. Evidence arrays must be dense, with no missing cells. Numeric observation lists allow at most 10,000 entries, subject to any smaller bounds stated above. String lists allow at most 128 strings of at most 128 characters. Extremely large text is rejected.
Alternative or Complementary methods
For a related review, use Wash Sale Rule Does Not Apply to Crypto Loophole Status Lookup: A crypto wash-sale reference needs the jurisdiction, asset classification, transaction, and applicable date. This lookup retains your supplied authority record and does not presume that the title’s non-applicability claim is correct. For a complementary step, use Tax Loss Harvest Offset Limit Calculator: Eligible capital losses can be allocated first against gains and then against an independently applicable ordinary-income cap. Tracking the residual prevents unused losses from disappearing from the calculation.
References
-
Wash Sale Rule 30 Day Flag Checker — tool.io
Similar or alternative tools
- Wash Sale Rule Does Not Apply to Crypto Loophole Status Lookup
A crypto wash-sale reference needs the jurisdiction, asset classification, transaction, and applicable date. This lookup retains your supplied authority record and does not presume that the title’s non-applicability claim is correct.
- Tax Loss Harvest Offset Limit Calculator
Eligible capital losses can be allocated first against gains and then against an independently applicable ordinary-income cap. Tracking the residual prevents unused losses from disappearing from the calculation.