0s and 1s CIS calculators is listed as active in the registry but did not answer our last check. It exposes 7 tools. Last commit 18 Oct 2026.
Free UK CIS calculators: deductions, deadlines, late penalties, gross payment test, verification.
Uptime history
16 days of history · worst day 0%
16 days agonow
8.8%
Uptime 24h
8 of 91 checks
7
Tools
read from the server
821 ms
Response time
average over 24h
0
Stars
last commit 18 Oct 2026
What changed 1
Every tool that appeared, vanished or quietly changed what it asks for. Recorded since 19 October 2026. No other catalogue keeps this.
19 Oct
a tool changed version
0s and 1s CIS calculators does not always answer
Over the last week it answered 11.1% of our checks. We check every 15 minutes, so you hear about the next outage within the hour — not from your users.
Connect this server
Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 9 min ago.
run in your terminal
claude mcp add cis --transport http https://0sand1s.co.uk/mcpSettings → Connectors → Add custom connector, then paste this address
https://0sand1s.co.uk/mcp~/.codex/config.toml
[mcp_servers.cis]
url = "https://0sand1s.co.uk/mcp".cursor/mcp.json
{
"mcpServers": {
"cis": {
"url": "https://0sand1s.co.uk/mcp"
}
}
}.vscode/mcp.json
{
"servers": {
"cis": {
"type": "http",
"url": "https://0sand1s.co.uk/mcp"
}
}
}Available tools 7
Read directly from the server with tools/list, grouped by what they act on.
If a tool disappears, we record the date.
cis
cis_deduction
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).
cis_gross_payment_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.
cis_gross_up
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.
cis_late_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.
cis_needs_verification
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.
cis_nil_return_check
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.
cis_tax_month
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.
Endpoints
| URL | Transport | State | Latency | Checked |
|---|---|---|---|---|
| https://0sand1s.co.uk/mcp | streamable-http | answering | 80 ms | 9 min ago |
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0s and 1s CIS calculators — questions
Answers built from our own checks of this server.
What can 0s and 1s CIS calculators do?
It exposes 7 tools, read directly from the server on our last check. Among them: cis_deduction, cis_gross_payment_turnover_test, cis_gross_up, cis_late_penalties, cis_needs_verification, cis_nil_return_check and 1 more. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README.
How MCP servers expose tools in the first place →
Is 0s and 1s CIS calculators working right now?
We send a real MCP handshake every 15 minutes. Over the last 24 hours 8 of 91 checks got a reply (8.8%), average response time 821 ms. The bar chart above shows every period we have measured.
The registry lists 0s and 1s CIS calculators as active — why does it not respond?
The official MCP registry stores what the author submitted; it does not verify that the server still runs. We check the endpoint ourselves, and this one does not answer. Catalogues that copy the registry without checking will show it as working.
How do I connect 0s and 1s CIS calculators?
Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.
Does 0s and 1s CIS calculators need an API key?
No. 0s and 1s CIS calculators completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 7 of them are readable on this page. This is what we observed, not what the docs claim.
How fast is 0s and 1s CIS calculators?
It answers our handshake in 821 ms on average, which is faster than 10% of all working MCP servers we measure. That is on the slow side — worth knowing if the tool sits inside an interactive loop. The comparison comes from our own checks across the whole registry, every 15 minutes.
Is 0s and 1s CIS calculators open source?
The code is open source: it is published under the MIT licence, 0 stars on GitHub and 1 open issue. The licence covers the code in the repository, not the hosted service at 0sand1s.co.uk, which runs on its operator's own terms.