Part 3 · Reconciliation matching algorithm
A 7-tier cascade with confidence scoring and operator-banded review.
Each tier is a strict superset of the previous in expense; if a cheaper tier matches, stop. Confidence drops as we relax constraints. Below 60% - mandatory operator review. Engineers can read the pseudo-code; auditors can read the rule strings.
Exact
GSTIN == GSTIN AND invoice_no == invoice_no AND amount == amount
Auto-accept
Normalized
Same as exact, after strip-lowercase-pad invoice_no normalization on both sides
Auto-accept
FY-aware
Normalized + FY-token substitution (FY24-25 ↔ 2024-25 ↔ 24-25-FY)
Auto-accept
Tolerance
Normalized GSTIN + invoice_no, amount within max(₹1, 0.01%), date within ±7 days
Auto-accept; sample-audit 10%
Multi-month
Tolerance match against any 2B period within ±3 months from PR period
Surface for operator review
Fuzzy-GSTIN
Levenshtein(GSTIN_pr, GSTIN_2b) ≤ 1 AND same PAN segment AND invoice_no + amount match
Mandatory operator review
Unmatched
Nothing above fires
Surface for operator: chase supplier or write off
TypeScript-flavored pseudo-code
function match(prInvoice: InvoicePR, candidates2B: Invoice2B[]): MatchResult {
// Tier 1 - Exact
const exact = candidates2B.find(c =>
c.supplier_gstin === prInvoice.supplier_gstin &&
c.invoice_no === prInvoice.invoice_no &&
c.invoice_amount === prInvoice.invoice_amount
);
if (exact) return { type: 'exact', confidence: 100, matched: exact };
// Tier 2 - Normalized invoice_no
const norm = normalize(prInvoice.invoice_no); // lowercase + strip non-alphanumeric
const normMatch = candidates2B.find(c =>
c.supplier_gstin === prInvoice.supplier_gstin &&
normalize(c.invoice_no) === norm &&
c.invoice_amount === prInvoice.invoice_amount
);
if (normMatch) return { type: 'normalized', confidence: 95, matched: normMatch };
// Tier 3 - FY-token substitution
for (const variant of fyVariants(prInvoice.invoice_no)) {
const m = candidates2B.find(c =>
c.supplier_gstin === prInvoice.supplier_gstin &&
normalize(c.invoice_no) === normalize(variant) &&
c.invoice_amount === prInvoice.invoice_amount
);
if (m) return { type: 'fy_aware', confidence: 90, matched: m };
}
// Tier 4 - Tolerance bands
const tolerance = candidates2B.find(c =>
c.supplier_gstin === prInvoice.supplier_gstin &&
normalize(c.invoice_no) === norm &&
abs(c.invoice_amount - prInvoice.invoice_amount) <= max(1, 0.0001 * max(c.invoice_amount, prInvoice.invoice_amount)) &&
abs(daysBetween(c.invoice_date, prInvoice.invoice_date)) <= 7
);
if (tolerance) {
const categories = detectMismatchCategories(prInvoice, tolerance);
return { type: 'tolerance', confidence: 85, matched: tolerance, mismatchCategories: categories };
}
// Tier 5 - Multi-month lookback
const multiMonth = findInPeriodWindow(prInvoice, candidates2B, { months: 3 });
if (multiMonth) return { type: 'multi_month', confidence: 70, matched: multiMonth };
// Tier 6 - Fuzzy GSTIN (last resort before unmatched)
const fuzzy = candidates2B.find(c =>
samePAN(c.supplier_gstin, prInvoice.supplier_gstin) &&
levenshtein(c.supplier_gstin, prInvoice.supplier_gstin) <= 1 &&
normalize(c.invoice_no) === norm
);
if (fuzzy) return { type: 'fuzzy_gstin', confidence: 60, matched: fuzzy };
return { type: 'unmatched', confidence: 0, matched: null };
}