# 0s and 1s

> CIS filing web app for UK building contractors who pay subcontractors: verify subbies with HMRC, record payments with the CIS deduction worked out, file the monthly CIS300 return and nil returns, and send payment and deduction statements. Works on a computer or a phone.

30-day free trial with no card, then One firm £9 a month, Up to 3 firms £19 a month, excluding VAT. No per-return or nil-return fees. Returns are filed with the contractor's own Government Gateway login, which is never stored.

0s and 1s has applied for HMRC CIS recognition; the decision is pending. Help: support@0sand1s.co.uk.

## Features

- [Verify subbies](https://0sand1s.co.uk/verify-subbies): Check each subbie's rate with HMRC before you pay
- [Record payments](https://0sand1s.co.uk/record-payments): The deduction and net worked out on every payment
- [File the CIS300](https://0sand1s.co.uk/file-cis300): Monthly returns and nil returns, by the 19th
- [Send statements](https://0sand1s.co.uk/statements): Payment and deduction statements by email
- [Pricing](https://0sand1s.co.uk/pricing): Plans by number of firms, and the free trial
- [Security](https://0sand1s.co.uk/security): How the Government Gateway login, sign-in and each firm's records are kept safe
- [About](https://0sand1s.co.uk/about): Who built 0s and 1s, why it exists, and how to get help

## For developers and AI assistants

- [CIS API and MCP server](https://0sand1s.co.uk/developers): Free CIS calculators as a JSON API and an MCP server, with no key
MCP server (Streamable HTTP, no sign-in): https://0sand1s.co.uk/mcp
OpenAPI document: https://0sand1s.co.uk/api/v1/openapi.json

## Free CIS tools

- [CIS deduction calculator](https://0sand1s.co.uk/tools/cis-calculator): Work out the deduction from gross, materials and rate, or from a day rate
- [CIS penalty calculator](https://0sand1s.co.uk/tools/cis-penalty-calculator): What a late return costs, and the date each penalty is charged
- [CIS gross payment status checker](https://0sand1s.co.uk/tools/gross-payment-status-checker): Check the turnover test, and what else HMRC looks at

## CIS guides

- [What is CIS](https://0sand1s.co.uk/guides/what-is-cis): The Construction Industry Scheme in plain words: who it covers and what you do each month
- [CIS deadlines](https://0sand1s.co.uk/guides/cis-deadlines): Return by the 19th, payment by the 22nd if paid electronically
- [CIS nil returns](https://0sand1s.co.uk/guides/cis-nil-return): When you need one, and how to tell HMRC in advance you won't pay any subbies
- [CIS late filing penalties](https://0sand1s.co.uk/guides/cis-penalties): What a late return costs, and what makes it more
- [CIS changes from 6 April 2026](https://0sand1s.co.uk/guides/cis-changes-2026): Nil returns, public bodies, gross payment status and Making Tax Digital
- [Appeal a CIS late filing penalty](https://0sand1s.co.uk/guides/cis-penalty-appeal): The 30 days you have, what counts as a reasonable excuse, and how to appeal
- [Verify a subcontractor](https://0sand1s.co.uk/guides/verify-a-subcontractor): When to verify, what you need and the three rates
- [CIS payment and deduction statements](https://0sand1s.co.uk/guides/cis-statements): What a statement must show and when it's due
- [Free CIS software](https://0sand1s.co.uk/guides/free-cis-software): What HMRC's free CIS service does, and what software adds
- [CIS and the VAT reverse charge](https://0sand1s.co.uk/guides/cis-reverse-charge): Who accounts for the VAT, and the CIS deduction on the same payment
- [CIS materials deduction](https://0sand1s.co.uk/guides/cis-materials): What counts as materials, plant hire included, and what doesn't
- [Register as a CIS contractor](https://0sand1s.co.uk/guides/register-as-a-cis-contractor): Who has to register, how, and what to do before paying your first subbie