# 0s and 1s CIS calculators (remote · 0sand1s.co.uk)

Free UK CIS calculators: deductions, deadlines, late penalties, gross payment test, verification.

- Trust score: 79/100 (medium)
- Change this week: +3
- Registry status: active
- Liveness: live
- Owner verified: no
- Last scored: 2026-11-05

## Components

- remote · `0sand1s.co.uk`: 79/100 (this document), [markdown](https://verifymcp.io/servers/uk-co-0sand1s-cis/0sand1s.md), [page](https://verifymcp.io/servers/uk-co-0sand1s-cis/0sand1s)

## Channel facts

- Endpoint: `https://0sand1s.co.uk/mcp`
- Transports: `streamable-http`
- Auth: `none`
- Version: `1.0.1`

## Trust breakdown

How this component scores in each security and reliability category. Every signal is checked automatically against the live server, and we only credit what we can confirm. Scores are 0–100 per category. Scoring method: https://verifymcp.io/docs/scoring (what has changed: https://verifymcp.io/docs/scoring/changelog)

Scored 2026-11-05.

- **Endpoint Security**: 80/100
  - The endpoint's TLS certificate is valid, in date, and uses a strong key.
  - No authorisation is required to call this server. Every tool declares its destructiveHint and none is destructive, so open access doesn't expose one.
  - HTTPS is enforced; there's no plaintext access path.
  - The HSTS (Strict-Transport-Security) header is present.
  - DNSSEC check failed: this domain isn't protected by DNSSEC.
- **Transport & Reachability**: 100/100
  - Verified streamable-http transport via a live MCP handshake.
- **Schema Quality & AI Usability**: 61/100
  - AI-judged instruction clarity (excellent).
  - Context-footprint check failed: tool/resource definitions use about 1985 tokens (~283/item across 7 items; 7 tools + 0 resources), over budget; trim descriptions and params.
  - Usage-examples check failed: none of the tools include examples.
- **Stability & Change Management**: 60/100
  - Stability observed for 18 of 30 days with no destabilising changes; credit accrues until the full window elapses.
- **Tool Coverage**: 100/100
  - 100% of tools have a non-trivial description (not blank, and not just the tool's name).
  - 100% of tool parameters carry a description.
- **Tool Safety**: 100/100
  - No prompt-injection markers were found in the server instructions, tool names or descriptions we captured.
  - We read all 7 captured tool definition(s), and no name or description among them implies an irreversible operation.
  - An AI judge read all 8 captured unit(s) of tool text and found none that tries to manipulate the model reading it.
- **Capabilities**: 100/100
  - Implements a current MCP spec version (2026-07-28).

## Install

### How do I install the 0s and 1s CIS calculators MCP server?

0s and 1s CIS calculators is a hosted endpoint at https://0sand1s.co.uk/mcp, so there is nothing to install locally. Ready-made configuration for Claude, Cursor, VS Code, Codex and 5 more is on this page, copied from each client's own documentation.

### Claude

```bash
claude mcp add --transport http uk-co-0sand1s-cis 'https://0sand1s.co.uk/mcp'
```

### Cursor

```json
{
  "mcpServers": {
    "uk-co-0sand1s-cis": {
      "url": "https://0sand1s.co.uk/mcp"
    }
  }
}
```

### VS Code

```json
{
  "servers": {
    "uk-co-0sand1s-cis": {
      "type": "http",
      "url": "https://0sand1s.co.uk/mcp"
    }
  }
}
```

### Codex

```toml
[mcp_servers.uk-co-0sand1s-cis]
url = "https://0sand1s.co.uk/mcp"
```

### opencode

```json
{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "uk-co-0sand1s-cis": {
      "type": "remote",
      "url": "https://0sand1s.co.uk/mcp",
      "enabled": true
    }
  }
}
```

### OpenClaw

```bash
openclaw mcp add uk-co-0sand1s-cis --url 'https://0sand1s.co.uk/mcp' --transport streamable-http
```

### Hermes

```yaml
mcp_servers:
  uk-co-0sand1s-cis:
    url: "https://0sand1s.co.uk/mcp"
```

### Netclaw

```json
{
  "McpServers": {
    "uk-co-0sand1s-cis": {
      "Transport": "http",
      "Url": "https://0sand1s.co.uk/mcp"
    }
  }
}
```

### Vellum

```bash
assistant mcp add uk-co-0sand1s-cis -t streamable-http -u 'https://0sand1s.co.uk/mcp'
```

### Other

```json
{
  "mcpServers": {
    "uk-co-0sand1s-cis": {
      "type": "http",
      "url": "https://0sand1s.co.uk/mcp"
    }
  }
}
```

The mcpServers block is a cross-client convention. Remote transports vary, so check your client's docs.

## Changelog

Every change recorded for this component, newest first. Days that predate change tracking, or that we cannot explain, say so: "we were watching and nothing happened" and "we were not watching" are different claims.

### 2026-11-04 (score 79, +1)

No change was recorded against any check on this day. Stability & Change Management went from 53 to 57. That category is still filling its 30-day observation window: 16 days of observed history at the previous scan, 17 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-11-01 (score 78, +1)

No change was recorded against any check on this day. Stability & Change Management went from 43 to 47. That category is still filling its 30-day observation window: 13 days of observed history at the previous scan, 14 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-30 (score 77, +1)

No change was recorded against any check on this day. Stability & Change Management went from 37 to 40. That category is still filling its 30-day observation window: 11 days of observed history at the previous scan, 12 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-28 (score 76, +1)

No change was recorded against any check on this day. Stability & Change Management went from 30 to 33. That category is still filling its 30-day observation window: 9 days of observed history at the previous scan, 10 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-26 (score 75, +1)

No change was recorded against any check on this day. Stability & Change Management went from 23 to 27. That category is still filling its 30-day observation window: 7 days of observed history at the previous scan, 8 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-24 (score 74, +1)

No change was recorded against any check on this day. Stability & Change Management went from 17 to 20. That category is still filling its 30-day observation window: 5 days of observed history at the previous scan, 6 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-22 (score 73, +1)

No change was recorded against any check on this day. Stability & Change Management went from 10 to 13. That category is still filling its 30-day observation window: 3 days of observed history at the previous scan, 4 at this one. The score rises as the window fills, whether or not the server changes.

### 2026-10-20 (score 72, +1)

No change was recorded against any check on this day. Stability & Change Management went from 3 to 7. That category is still filling its 30-day observation window: 1 days of observed history at the previous scan, 2 at this one. The score rises as the window fills, whether or not the server changes.

## MCP tools (7)

### `cis_deduction` (~306 tokens)

CIS deduction, gross to net

Works out the CIS deduction on a payment to a subcontractor, from the gross bill to the net payment. Takes the gross including VAT, the VAT, the subcontractor's materials and the rate (0, 20 or 30). VAT is never taxed under CIS and materials come off before the rate applies; the deduction is rounded down to the penny. Returns each step of the working, money in pence and pounds. Does not cover retentions, or decide which rate applies (verify the subcontractor with HMRC for that).

Input parameters:

- `gross` (string, required): The amount being paid, including any VAT, before the CIS deduction. Pounds, as a string like "1,200.00" or a number like 1200.
- `materials` (string): What the subcontractor paid for materials, plant hire, consumables and fuel (not travel) on the job. Without VAT if the subcontractor is VAT registered, with it if not. Pounds, as a string like "1,20…
- `rate` (integer, required): The subcontractor's CIS rate in per cent: 20 if registered, 30 if not registered or unmatched when verified, 0 for gross payment status
- `vat` (string): The VAT within the gross. Leave out or 0 under the domestic reverse charge. Pounds, as a string like "1,200.00" or a number like 1200.

### `cis_gross_up` (~237 tokens)

CIS gross up, net to gross

Finds the gross amount (excluding VAT) that leaves a given net payment after the CIS deduction, for a subcontractor quoted a take-home figure. Takes the net, the subcontractor's materials and the rate (0, 20 or 30). Where rounding lets two grosses give the same net, the larger is returned so CIS is never under-deducted. Returns the forward working on that gross, money in pence and pounds. VAT is not included; add it on top if the subcontractor charges it.

Input parameters:

- `materials` (string): The subcontractor's materials within the payment, as for cis_deduction. Pounds, as a string like "1,200.00" or a number like 1200.
- `net` (string, required): The payment the subcontractor should receive after the CIS deduction, excluding VAT. Pounds, as a string like "1,200.00" or a number like 1200.
- `rate` (integer, required): The subcontractor's CIS rate in per cent: 20 if registered, 30 if not registered or unmatched when verified, 0 for gross payment status

### `cis_tax_month` (~145 tokens)

CIS tax month and deadlines

For a date, gives the CIS tax month it falls in (the 6th to the 5th), the tax year, the date the monthly return (CIS300) is due (the 19th, also the date for paying HMRC by any means other than electronically), and the date for paying HMRC electronically (the 22nd, moved back to the banking day before when the 22nd is a weekend or an England and Wales bank holiday). Bank holidays are known to bank_holidays_known_until; after that only weekends move the date.

Input parameters:

- `date` (string, required): Any date, such as a payment date or today, YYYY-MM-DD

### `cis_late_penalties` (~358 tokens)

CIS late filing penalties

Works out the late filing penalties on one monthly CIS return under Finance Act 2009 Schedule 55: £100 the day after the 19th, £200 at 2 months, then the greater of £300 and 5% of the deductions at 6 and at 12 months (5% alone for a first return). Takes the tax year and month, the filing date or none, today's date, the deductions and whether a return had been filed before. Returns each penalty with its date and whether it is charged, avoided or still to come. Does not cover deliberate withholding, interest on late payment, or appeals.

Input parameters:

- `as_at` (string, required): Today's date. Penalties on a return not yet filed run to this date, YYYY-MM-DD
- `deductions` (string): The CIS deductions the return shows, or would show. Leave out or 0 for a nil return. Pounds, as a string like "1,200.00" or a number like 1200.
- `filed_before` (boolean): true if the contractor had already filed a CIS return before this one was due (the usual case). false for the first return, which has no £300 minimum
- `filed_on` (string): The day the return was filed. Leave out or null if it has not been filed, YYYY-MM-DD
- `tax_month` (integer, required): The tax month, 1 to 12: 1 is 6 April to 5 May, 12 is 6 March to 5 April
- `tax_year` (integer, required): The tax year, by the calendar year it starts in: 2026 for 6 April 2026 to 5 April 2027

### `cis_gross_payment_turnover_test` (~295 tokens)

CIS gross payment status turnover test

Checks the turnover test for CIS gross payment status (Finance Act 2004 Schedule 11, SI 2005/2045 reg 28): £30,000 net construction turnover for a sole trader; for a partnership or company, the lower of £30,000 for each partner or relevant person and £100,000. In a close company, shareholders count as well as directors. Returns the figure needed by each route, which one applies, and how far short. Covers the turnover test only, not the business test or the compliance test.

Input parameters:

- `business_type` (string, required): The subcontractor's business: sole-trader, partnership or company
- `close_company` (boolean): Company only: true if it is a close company (controlled by 5 or fewer people, or by its directors)
- `directors` (integer): Company only: the number of directors, the highest at any one time in the 12 months
- `net_turnover` (string, required): Construction turnover for the last 12 months, less VAT and the cost of materials. Pounds, as a string like "1,200.00" or a number like 1200.
- `partners` (integer): Partnership only: the number of partners, the highest at any one time in the 12 months
- `shareholders` (integer): Close company only: shareholders who are not also directors, each counted once

### `cis_needs_verification` (~217 tokens)

Does a CIS subcontractor need verifying?

Says whether a contractor must verify a subcontractor with HMRC before paying them (SI 2005/2045 reg 6): not needed if the subcontractor was on one of this contractor's CIS returns, or was verified by this contractor, in the tax year of the payment or the two before. Takes the payment date, the tax years the subcontractor was on a return and the last verification date, all supplied by the caller. Does not contact HMRC or verify anyone, and does not cover group companies or business transfers.

Input parameters:

- `included_on_return_in_tax_years` (array): Tax years (by the year each starts in) in which this contractor included the subcontractor on a CIS return. An array, or comma-separated like "2025,2026"
- `last_verified_on` (string): The date this contractor last verified the subcontractor with HMRC, if ever, YYYY-MM-DD
- `payment_date` (string, required): The date of the payment about to be made, YYYY-MM-DD

### `cis_nil_return_check` (~332 tokens)

Is a CIS nil return due?

Says whether a contractor must file a CIS nil return for a tax month (SI 2005/2045 reg 4(9A) and (9B), inserted by SI 2026/289 from 6 April 2026): due when a mainstream contractor that has paid subcontractors before pays none that month, unless it told HMRC no later than 14 days before the month started. Takes the tax year and month and yes or no answers. Returns whether a nil return is due, why, and the date it is due. Does not file anything.

Input parameters:

- `mainstream_contractor` (boolean): true for a mainstream contractor (a construction business). false for a deemed contractor, which is outside the nil return rule
- `paid_subcontractors_before` (boolean, required): true if the contractor had paid any subcontractor before that tax month started
- `paid_subcontractors_in_month` (boolean, required): true if any subcontractor was paid in that tax month, gross payments included
- `tax_month` (integer, required): The tax month, 1 to 12: 1 is 6 April to 5 May, 12 is 6 March to 5 April
- `tax_year` (integer, required): The tax year, by the calendar year it starts in: 2026 for 6 April 2026 to 5 April 2027
- `told_hmrc_no_payments_on` (string): If the contractor told HMRC in advance that no payments would be made in that month, the date it did so. Leave out if not, YYYY-MM-DD

## Diagnostics

Captured diagnostic sections: TLS, DNSSEC, Authorisation, Transports. The full working is on the page: https://verifymcp.io/servers/uk-co-0sand1s-cis/0sand1s#diagnostics

## Score history

- 2026-11-05: 79
- 2026-11-04: 79
- 2026-11-03: 78
- 2026-11-02: 78
- 2026-11-01: 78
- 2026-10-31: 77
- 2026-10-30: 77
- 2026-10-29: 76
- 2026-10-28: 76
- 2026-10-27: 75
- 2026-10-26: 75
- 2026-10-25: 74
- 2026-10-24: 74
- 2026-10-23: 73
- 2026-10-22: 73
- 2026-10-21: 72
- 2026-10-20: 72
- 2026-10-19: 71
- 2026-10-18: 71

## Common questions

### What is the 0s and 1s CIS calculators MCP server?

0s and 1s CIS calculators is an MCP server listed in the public MCP registry as uk.co.0sand1s/cis. Free UK CIS calculators: deductions, deadlines, late penalties, gross payment test, verification. This page covers its hosted endpoint (https://0sand1s.co.uk/mcp).

### Is the 0s and 1s CIS calculators MCP server safe to use?

0s and 1s CIS calculators scores 79 out of 100 on VerifyMCP. That is a record of what we were able to check automatically, not an endorsement. The category breakdown on this page shows every signal behind the number, including the ones we could not confirm.

### What tools does the 0s and 1s CIS calculators MCP server expose?

0s and 1s CIS calculators exposes 7 tools: cis_deduction, cis_gross_up, cis_tax_month, cis_late_penalties, cis_gross_payment_turnover_test, and 2 more. Their descriptions and schemas cost roughly 1,890 tokens of context every time the server is loaded.

### Does the 0s and 1s CIS calculators MCP server require authentication?

No. We connected to 0s and 1s CIS calculators without credentials and it answered, so anything it exposes is reachable by anyone who knows the address.

### Is the 0s and 1s CIS calculators MCP server still maintained?

0s and 1s CIS calculators is still listed as active in the MCP registry. We last reached this channel on 5 November 2026. Those dates come from our own scans of the registry and the channel itself, not from anything the publisher announced.

## Links

- Remote endpoint: https://0sand1s.co.uk/mcp
- Repository: https://github.com/0sand1s-uk/cis-mcp
- Website: https://0sand1s.co.uk/developers
- Changelog RSS feed: https://verifymcp.io/servers/uk-co-0sand1s-cis/0sand1s.xml
- Changelog JSON feed: https://verifymcp.io/servers/uk-co-0sand1s-cis/0sand1s.json
- HTML version of this page: https://verifymcp.io/servers/uk-co-0sand1s-cis/0sand1s