Compute Russian VAT (НДС): add on top of net or extract from gross (NK RF art. 164, 168).

When to use

• Invoice line: net→gross (mode=add) or gross→net+VAT (mode=extract).

• USN taxpayers on special VAT rates 5% or 7% (from 2025 rules).

• Quick sanity check before bookkeeping export.

When NOT to use

• VAT declaration filing, multi-rate invoices, or export/zero-rate cases.

• Mixed taxable/exempt lines — sum per line in accounting software.

Parameters

• amount: base sum in RUB (net for add, gross for extract).

• rate: 20, 10, 0, 5, or 7 (percent).

• mode: add | extract.

Returns: {net, vat, gross, rate, mode, formula, article, disclaimer, snapshot_date}.

Limitations: read-only, offline, single-rate line; no side effects. Example: amount=100000, rate=20, mode=add → vat=20000, gross=120000.

Calculate simplified tax (USN/УСН): 6% on income or 15% income-minus-expense with minimum tax (NK RF ch. 26.2).

When to use

• Estimate USN tax for a quarter/year before payment.

• Object income (6%): deduct paid IP contributions (capped at 50% if has_employees).

• Object income_minus_expense (15%): apply minimum tax 1% of income if 15% base is lower.

When NOT to use

• Exact advance-payment calendar or KKT cash reporting.

• Taxpayers above USN income limits — check get_rates for limits first.

Parameters: income, obj, expenses, rate (regional override), contributions_paid, has_employees, advances_paid.

Returns: {tax, base, rate, min_tax, contributions_deduction, advances, formula, article, disclaimer}.

Limitations: read-only, offline; regional rates optional; subtracts advances_paid from result.

IP fixed insurance contributions + 1% on income above 300k RUB (NK RF art. 430).

When to use: annual IP self-contribution estimate; set months<12 for partial year. When NOT to use: employee payroll — use payroll tools; amounts for closed years without snapshot check. Side effects: read-only, deterministic, offline; rates from bundled snapshot.

Returns: {fixed, extra_1pct, total, income, year, months, formula, article, disclaimer}.

Progressive personal income tax (NDFL/НДФЛ) 2025+ with per-bracket breakdown (NK RF art. 224).

When to use: estimate annual NDFL on salary or IP income after deductions. When NOT to use: monthly withholding by employer — use payroll; non-resident rates not modeled. Side effects: read-only, deterministic, offline; no auth or network.

Returns: {tax_total, taxable_base, brackets[], formula, article, disclaimer, snapshot_date}.

Patent taxation (PSN/ПСН) cost: potential income × 6% × months/12 minus contributions (NK RF ch. 26.5).

When to use: compare patent cost vs USN for an activity; potential_income from regional law. When NOT to use: eligibility/OKVED limits — verify with FNS; employee-heavy cases need manual review. Side effects: read-only, deterministic, offline; no auth or network.

Returns: {patent_cost, before_deduction, contributions_deduction, months, formula, article, disclaimer}.

Estimate late-payment tax penalty (пени) per NK RF art. 75 using the CBR key rate.

When to use

• Quick what-if: how much penalty accrues on a known arrears amount and delay in days.

• Org vs IP/individual: orgs use 1/300 for days 1–30, then 1/150; IP and individuals use 1/300 for all days.

• Before a payment plan or negotiation — ballpark figure, not a filing document.

When NOT to use

• Multi-period calculation where the key rate changed during the delay (this tool uses one flat rate).

• Penalties on non-tax debts (commercial loans, fines outside NK art. 75).

• Official amount on a tax notice — always take the figure from FNS/LK; use this tool only for estimates.

Parameters

• amount: principal arrears in RUB (non-negative).

• days: calendar days of delay (0 → penalty 0).

• key_rate: annual CBR %; omit to use bundled snapshot default (response includes warning_ru if default used).

• payer: org | ip | individual — selects the 1/300 vs 1/150 split for legal entities.

Returns (dict)

• penalty (float): total penalty in RUB, rounded to kopecks.

• amount, days, key_rate, payer: echo inputs used in the formula.

• formula (str): human-readable breakdown.

• article: "ст. 75 НК РФ".

• snapshot_date, disclaimer, source: metadata for audit trail.

• warning_ru (optional): present when key_rate was taken from snapshot, not passed explicitly.

Limitations

• Single key rate for the whole period; for rate changes call get_rates(fresh=true) and run per sub-period manually.

• Does not include other sanctions (штрафы) under NK art. 122/123 — only пени art. 75.

• Read-only, offline, deterministic; no side effects; idempotent for identical inputs.

Examples

• Org, 100_000 RUB, 45 days, key_rate=21: days 1–30 @ amount×21%/300×30 + days 31–45 @ amount×21%/150×15.

• IP, 50_000 RUB, 10 days: amount×rate%/300×10 for all days.

• days=0 → penalty=0 regardless of amount.

Tax rates and limits: offline snapshot (default) or live hosted pull (fresh=true, Pro key).

When to use

• Before calc_penalty: pass fresh CBR key_rate or read cbr_key_rate_default from snapshot.

• Before calc_usn/calc_insurance_ip: verify USN income limits and IP contribution fixed amounts.

• kinds filter narrows response: cbr_key_rate | ip_fixed_contrib | usn_limits | ndfl_scale | deflator.

When NOT to use

• Legal interpretation of limits — snapshot may lag; use fresh=true for production DD.

Parameters

• fresh: false (default) = bundled snapshot, no network; true = hosted API (MCP_FNS_CALC_TOKEN).

• kinds: optional list to subset tables.

Returns: rate tables, snapshot_date (offline) or live payload + disclaimer.

Limitations: fresh=true requires Pro token; snapshot date fixed at package build time.

Check self-employed (NPD/НПД) status by taxpayer INN via FNS open data. Requires Pro API key.

When to use: before paying a sole proprietor as individual — mandatory NPD verification. When NOT to use: offline what-if math — use calculators; without token returns missing_token error. Side effects: read-only HTTPS to hosted backend; no local data mutation. Needs MCP_FNS_CALC_TOKEN.

Returns: {is_selfemployed, inn, checked_at, source, disclaimer} or error/missing_token.

IP registration status, OKVED and EGRIP dates by 12-digit INN. Requires Pro API key.

When to use: confirm counterparty is active IP before contract/payment. When NOT to use: full EGRUL extract — use mcp-egrul; offline mode unavailable. Side effects: read-only HTTPS; needs MCP_FNS_CALC_TOKEN.

Returns: {status, inn, okved, registration_date, ... disclaimer} or error.

Match against FNS disqualified persons register by INN or FIO. Requires Pro API key.

When to use: compliance screen before appointing director/signatory; provide inn or fio. When NOT to use: sole evidence for legal decisions — result is indicative, verify manually. Side effects: read-only HTTPS; needs MCP_FNS_CALC_TOKEN. At least one of inn/fio required.

Returns: {matches[], query, disclaimer} or validation/error.

Bank account operation suspension info from FNS (10–12 digit INN). Requires Pro API key.

When to use: treasury/compliance check before large outbound payment. When NOT to use: real-time bank balance — different service; offline unavailable. Side effects: read-only HTTPS; needs MCP_FNS_CALC_TOKEN.

Returns: {suspended, inn, details, disclaimer} or error.

Tax arrears / debt flags from FNS Transparent Business open data. Requires Pro API key.

When to use: counterparty due diligence alongside mcp-fns-check; 10–12 digit INN. When NOT to use: official debt certificate — request from FNS; offline unavailable. Side effects: read-only HTTPS; needs MCP_FNS_CALC_TOKEN.

Returns: {has_arrears, inn, amounts[], disclaimer} or error.