Suites · construction
Construction and trades
For builders, trades and contractors: quotes, materials take-offs, valuations with retention, CIS deductions, VAT reverse charge and Construction Act payment dates.
60 capabilities (28 core, 32 optional) and 13 gaps, in build order. Put each line in the file that calls it, then fune build.
UK first: CIS, the VAT domestic reverse charge and Construction Act payment dates follow UK legislation; it is not legal or tax advice.
Calculates tax from published rules; it is not tax advice. Have an accountant check how the app uses it before anyone files a return.
TypeScript Python Rust
1. Quotes and estimates
Price a job from labour, materials and markup.
construction.day-rate-quote core
A quote from labour days at a day rate, materials with a markup, and VAT.
A trade quote from labour days at a day rate, materials with a markup, and VAT.
fune!(construction.day-rate-quote@^1 ); // then call day_rate_quote(…)
1.0.0
finance.markup-price optional
Selling price from a cost and a target margin or markup.
Selling price from a cost and a target margin or markup in basis points, with explicit rounding.
fune!(finance.markup-price@^1 ); // then call markup_price(…)
1.0.0
quote-documents Producing the quote or estimate document (PDF, e-signature acceptance) is yours.
2. Materials take-off
Work out the materials a job needs.
construction.materials-area core
Packs of tiles, paint, plasterboard or flooring for an area, with waste and coats.
Packs of tiles, paint, plasterboard or flooring to cover an area, with waste and coats, rounded up to whole packs.
fune!(construction.materials-area@^1 ); // then call materials_area(…)
1.0.0
construction.brick-count optional
Bricks and mortar for a wall, openings subtracted, for UK standard bricks.
Bricks and mortar for a wall, openings subtracted, for UK standard 215 x 102.5 x 65 mm bricks with 10 mm joints.
fune!(construction.brick-count@^1 ); // then call brick_count(…)
1.0.0
construction.concrete-volume optional
Concrete for slabs, footings, pads and columns, and the order rounded up.
Concrete for slabs, strip footings, pads and round columns: volume to the litre and an order rounded up to 0.1 m³.
fune!(construction.concrete-volume@^1 ); // then call concrete_volume(…)
1.0.0
construction.timber-length optional
A cutting list: which stock lengths to buy and what to cut from each, with kerf.
Cutting list: which stock lengths to buy and which pieces to cut from each, allowing for saw kerf.
fune!(construction.timber-length@^1 ); // then call timber_cutting_list(…)
1.0.0
construction.roof-pitch optional
Roof pitch, rafter length and slope area from span, rise and length.
Roof pitch in degrees, rafter length and roof slope area from span, rise and length.
fune!(construction.roof-pitch@^1 ); // then call roof_pitch(…)
1.0.0
units.convert optional
Converts metric and imperial lengths, areas and volumes exactly.
Convert length, mass, area, volume, temperature and energy between units, exactly, as decimal text.
fune!(units.convert@^1 ); // then call convert_units(…)
1.0.0
property.floor-area optional Unreviewed
Floor area from room dimensions, in square metres and square feet.
Floor area from room lengths and widths, exactly, with the total in both square metres and square feet.
fune!(property.floor-area@^1 ); // then call floor_area(…)
1.0.2
supplier-prices Live prices and stock from builders' merchants: you supply pack prices.
3. Valuations and payments
Bill work done on account and pay subcontractors correctly.
construction.valuation core
Interim valuation: gross value to date, retention, previous payments, amount due, VAT and CIS.
Interim valuation: gross value to date, retention, previous payments, amount due, VAT or reverse charge, and CIS.
fune!(construction.valuation@^1 ); // then call interim_valuation(…)
1.0.0
construction.retention core
Retention held and released: full rate, half at practical completion, none at the end.
Retention held and released on a construction valuation: full rate, half at practical completion, none at the end.
fune!(construction.retention@^1 ); // then call retention(…)
1.0.0
construction.cis-deduction core
Construction Industry Scheme deduction (0, 20 or 30%) on the labour part of a payment.
Construction Industry Scheme deduction (0, 20 or 30%) on the labour part of a subcontractor payment.
fune!(construction.cis-deduction@^1 ); // then call cis_deduction(…)
1.0.2
construction.vat-reverse-charge core
Whether the VAT domestic reverse charge applies to a supply, and the invoice wording.
Whether the UK VAT domestic reverse charge applies to a construction supply, and the invoice wording.
fune!(construction.vat-reverse-charge@^1 ); // then call domestic_reverse_charge(…)
1.0.2
construction.payment-notice-dates core
Construction Act dates: payment due, payment notice, final date and pay-less notice.
Construction Act default dates: payment due, payment notice, final date for payment and pay-less notice.
fune!(construction.payment-notice-dates@^1 ); // then call payment_notice_dates(…)
1.0.2
cis-verification Verifying subcontractors with HMRC and filing the monthly CIS return (online) are not in caps.
4. Jobs and scheduling
Plan the days a job takes.
dates.add-business-days optional
Moves a start date by working days for a programme of works.
Move a date forward or back by working days, skipping weekends and a caller-supplied holiday list.
fune!(dates.add-business-days@^1 ); // then call add_business_days(…)
1.0.0
job-scheduling Scheduling crews and jobs, site diaries and photos.health-and-safety RAMS, permits and site inductions are not in caps.
Hold money as currency-tagged integer minor units and do plain arithmetic on it safely.
money.amount core
The Money type ({ minor, currency }) every other money capability takes and returns.
A currency-tagged monetary amount held in integer minor units.
fune!(money.amount@^1 ); // then call money(…)
1.0.2
money.add core
Adds and subtracts amounts, refusing to mix currencies by accident.
Add, subtract and negate monetary amounts, refusing to mix currencies.
fune!(money.add@^1 ); // then call add_money(…)
1.0.1
money.sum core
Totals a list of amounts, with an explicit currency for an empty list.
Total a list of monetary amounts, with an explicit currency for the empty case.
fune!(money.sum@^1 ); // then call sum_money(…)
1.0.1
money.compare core
Compares, mins, maxes and clamps amounts of one currency without unwrapping them.
Compare two amounts of one currency, refusing to compare across currencies; min, max and clamp too.
fune!(money.compare@^2 ); // then call compare_money, min_money, max_money, clamp_money
2.0.04 functions
6. Rates and rounding from money-basics
Apply percentages and divide amounts with the rounding stated, never a float.
money.apply-rate core
Applies a basis-point rate (VAT, discount, commission) to an amount with explicit rounding.
Apply a rate expressed in basis points to a monetary amount, with an explicit rounding mode.
fune!(money.apply-rate@^1 ); // then call apply_rate(…)
1.0.1
math.round-div core
Integer division with a named rounding mode, for any money maths the others do not cover.
Integer division with an explicit rounding mode, for money arithmetic that must not drift.
fune!(math.round-div@^1 ); // then call round_div(…)
1.0.0
math.basis-points optional
Converts "12.5%" to and from basis points exactly, for rates typed in by users.
Convert a rate between percent, basis points and a plain ratio exactly, as decimal text or integer basis points.
fune!(math.basis-points@^2 ); // then call convert_rate, to_basis_points, from_basis_points
2.0.03 functions
math.percent-change optional
Percentage change between two figures in basis points, for "up 4.2% on last month".
Percentage change from one value to another, in basis points, with an explicit rounding mode.
fune!(math.percent-change@^1 ); // then call percent_change(…)
1.0.0
math.rational optional
Exact fractions for rates that must not drift across many steps.
Exact fraction arithmetic, always reduced, for rates and ratios that must not drift.
fune!(math.rational@^2 ); // then call calculate_rational, rational, add_rational, subtract_rational, multiply_rational, divide_rational, compare_rational, rational_to_integer
2.0.08 functions
math.round-div-big optional
Rounded division on numbers past 2^53, for very large totals.
Divide two integers of any size with an explicit rounding mode, on decimal strings, for exact money sums past 2^53.
fune!(math.round-div-big@^1 ); // then call round_div_big(…)
1.0.0
Divide an amount between people, periods or lines so the parts add back to the whole.
money.allocate core
Splits an amount by ratios (60/40, by quantity) without losing or inventing a penny.
Split an amount across ratios without losing or inventing a single minor unit.
fune!(money.allocate@^1 ); // then call allocate(…)
1.0.1
money.split-even optional
Splits an amount into n near-equal parts that sum exactly, for instalments or shares.
Split an amount into n near-equal parts that add back up to exactly the whole.
fune!(money.split-even@^1 ); // then call split_even(…)
1.0.0
8. Display and input from money-basics
Show amounts to people and read what they type.
money.format core
Renders an amount as text with the currency's real number of decimal places.
Render a monetary amount as text, using the currency's real minor-unit precision.
fune!(money.format@^1 ); // then call format_money(…)
1.0.0
money.parse optional
Reads "£1,234.50" or "1.234,50 €" typed by a user into minor units, strictly.
Parse "£1,234.50" or "1.234,50 €" into integer minor units, strictly: no guessing, no rounding.
fune!(money.parse@^1 ); // then call parse_money(…)
1.0.0
money.currency-digits optional
How many decimal places each ISO 4217 currency has, for input boxes and validation.
How many decimal places a currency's minor unit has, from the ISO 4217 list.
fune!(money.currency-digits@^1 ); // then call currency_digits(…)
1.0.0
9. Other currencies from money-basics
Convert between currencies at a rate you hold.
money.convert optional
Converts an amount at a supplied exact rate with explicit rounding.
Convert an amount to another currency at a supplied exact rate, with an explicit rounding mode.
fune!(money.convert@^1 ); // then call convert_money(…)
1.0.0
10. Calendar arithmetic from dates-basics
Move and measure ISO dates exactly, with no date library and no clock reads.
dates.add-days core
Shifts a date by whole days, for due dates and windows.
Shift an ISO date by a whole number of days, forwards or backwards, with exact calendar arithmetic.
fune!(dates.add-days@^1 ); // then call add_days(…)
1.0.0
dates.add-months core
Adds months clamping to month end, so 31 January plus a month is the end of February.
Add calendar months to an ISO date, clamping to the month end: 31 Jan + 1 month is 28 or 29 Feb.
fune!(dates.add-months@^1 ); // then call add_months(…)
1.0.0
dates.days-between core
Signed calendar days between two dates, for ages of invoices and stays.
Calendar days from one ISO date to another, signed: negative when the second date is earlier.
fune!(dates.days-between@^1 ); // then call days_between(…)
1.0.0
dates.month-boundaries core
First and last day of a date's month, for monthly periods and statements.
The first day, last day and length of the calendar month containing a date.
fune!(dates.month-boundaries@^1 ); // then call month_boundaries(…)
1.0.0
dates.day-of-week core
ISO weekday of a date, for weekend rules and opening hours.
The ISO 8601 day of the week for a date: 1 is Monday through 7 is Sunday.
fune!(dates.day-of-week@^1 ); // then call day_of_week(…)
1.0.0
dates.is-leap-year optional
Whether a year is a leap year, for 365/366-day calculations.
Whether a year is a Gregorian leap year: every 4th, except centuries, except every 400th.
fune!(dates.is-leap-year@^1 ); // then call is_leap_year(…)
1.0.0
dates.overlap optional
Days two date ranges share, for prorating and clash checks.
Days two date ranges have in common, with the end of each range stated as inclusive or exclusive.
fune!(dates.overlap@^1 ); // then call overlap_days(…)
1.0.0
dates.age optional
Age in whole years on a date, handling 29 February birthdays.
Age in whole years on a given date, with 29 February birthdays ageing on 1 March in other years.
fune!(dates.age@^1 ); // then call age(…)
1.0.0
11. Periods and reporting dates from dates-basics
Put dates into the periods reports are grouped by.
dates.quarter core
Calendar and fiscal quarter of a date for any year-start month.
Calendar quarter and fiscal quarter of a date, with the fiscal year and quarter date ranges, for any start month.
fune!(dates.quarter@^1 ); // then call quarter(…)
1.0.0
dates.week-number optional
ISO week number and week-year, for weekly reports.
ISO 8601 week number and week-numbering year of a date: weeks start Monday, week 1 holds the first Thursday.
fune!(dates.week-number@^1 ); // then call week_number(…)
1.0.0
dates.day-count-fraction optional
Year fraction by ACT/365F, ACT/360, 30/360 or ACT/ACT, for interest periods.
Year fraction between two dates by ACT/365F, ACT/360, 30/360, 30E/360 or ACT/ACT ISDA, as an exact fraction.
fune!(dates.day-count-fraction@^1 ); // then call day_count_fraction(…)
1.0.0
12. Working days and holidays from dates-basics
Skip weekends and public holidays when counting or adding days.
dates.bank-holidays core
UK bank holidays for a region and year, as gov.uk publishes them.
UK bank and public holidays for a region and year, as published by gov.uk, including one-off holidays.
fune!(dates.bank-holidays@^1 ); // then call bank_holidays(…)
1.0.1
dates.business-days-between core
Working days between two dates, for SLAs and notice periods.
Working days between two dates, excluding weekends and a caller-supplied holiday list.
fune!(dates.business-days-between@^1 ); // then call business_days_between(…)
1.0.0
13. Repeating schedules from dates-basics
Generate the dates of something that repeats.
dates.recurrence optional
The next n dates of a rule: monthly on the 31st, last Friday, every two weeks.
The next n dates of a repeating rule: monthly on a day, last weekday of the month, every k days or weeks, yearly.
fune!(dates.recurrence@^1 ); // then call recurrence(…)
1.0.0
14. Times and durations from dates-basics
Work with times of day, durations and timestamps.
time.duration optional
Parses and adds durations like 1h30m in whole minutes, and formats the total.
Parse durations written as 1h30m, 90m or 01:30, add them up in whole minutes, and format the total.
fune!(time.duration@^1 ); // then call duration(…)
1.0.0
time.minutes-between optional
Minutes between two local date-times, across midnight.
Minutes from one local date and time to another, correct across midnight; wall-clock time, no time zones.
fune!(time.minutes-between@^1 ); // then call minutes_between(…)
1.0.0
time.round-to-increment optional
Rounds minutes to a billing increment such as 6 or 15.
Round a duration in minutes to a billing increment such as 6 or 15 minutes, up, down or to nearest.
fune!(time.round-to-increment@^1 ); // then call round_to_increment(…)
1.0.0
time.iso-to-unix optional
RFC 3339 timestamps to Unix seconds.
An RFC 3339 timestamp with a Z or offset, such as 2026-09-26T13:00:00+01:00, to Unix time in whole seconds.
fune!(time.iso-to-unix@^1 ); // then call iso_to_unix(…)
1.0.0
time.unix-to-iso optional
Unix seconds to an ISO 8601 UTC timestamp.
Unix time in seconds to an ISO 8601 UTC timestamp such as 2026-09-26T12:00:00Z, for years 0001 to 9999.
fune!(time.unix-to-iso@^1 ); // then call unix_to_iso(…)
1.0.0
time.countdown optional
Seconds left until a moment and a 4:05 style timer text.
Seconds left until a Unix time, whether it has passed, and a timer text like 4:05, for tokens or retry waits.
fune!(time.countdown@^1 ); // then call countdown(…)
1.0.0
15. VAT from uk-tax
Work out VAT from the dated rates HMRC publishes.
finance.tax.vat-rate core Unreviewed
The VAT rate in force for a jurisdiction, category and date; the others look it up.
Look up the VAT rate in force for a jurisdiction, category and date.
fune!(finance.tax.vat-rate@^1 ); // then call vat_rate(…)
1.2.2
finance.tax.add-vat core Unreviewed
Net to gross: VAT on a net amount at the rate on the date of supply.
Add VAT to a net amount using the rate in force on the date of supply.
fune!(finance.tax.add-vat@^1 ); // then call add_vat(…)
1.0.1
finance.tax.remove-vat core Unreviewed
Gross to net: the VAT already inside a VAT-inclusive price.
Extract the VAT already included in a gross amount, using the rate in force on the date of supply.
fune!(finance.tax.remove-vat@^1 ); // then call remove_vat(…)
1.0.2
finance.tax.vat-return optional Unreviewed
The nine-box VAT return totals for a period from categorised sales and purchases.
UK nine-box VAT return totals for a period from categorised sales and purchases (VAT Notice 700/12).
fune!(finance.tax.vat-return @^1 ); // then call vat_return(…)
1.0.1
finance.tax.vat-flat-rate optional Unreviewed
VAT due under the Flat Rate Scheme by business sector, for small businesses on it.
UK VAT Flat Rate Scheme: VAT due on gross turnover at the sector's dated rate, limited cost rate and first-year 1% off.
fune!(finance.tax.vat-flat-rate@^1 ); // then call flat_rate_vat(…)
1.0.1
16. Tax periods from uk-tax
Put dates into the UK periods tax is worked out over.
dates.uk-tax-year core
Which UK tax year (6 April to 5 April) a date falls in.
The UK personal tax year containing a date: 6 April to 5 April, with HMRC's label.
fune!(dates.uk-tax-year@^1 ); // then call uk_tax_year(…)
1.0.0
17. Tax identifiers from uk-tax
Check the numbers HMRC and Companies House issue before storing them.
validation.uk-vat-number core
Checks a UK VAT registration number's checksum.
Check a UK VAT registration number against HMRC's mod-97 checksum, including the post-2010 9755 variant.
fune!(validation.uk-vat-number@^1 ); // then call is_uk_vat_number(…)
1.0.0
validation.uk-utr optional
Checks a Unique Taxpayer Reference's check digit.
Check an HMRC Unique Taxpayer Reference's modulus 11 check digit, accepting the K and spacing people type.
fune!(validation.uk-utr@^2 ); // then call validate_uk_utr(…)
2.0.1
validation.uk-company-number optional
Checks and pads a Companies House company number.
Check a Companies House company number's format and prefix (SC, NI, OC, LP...) and zero-pad it to eight characters.
fune!(validation.uk-company-number@^2 ); // then call validate_uk_company_number(…)
2.0.1
Gaps What this kind of app usually needs that Functional Weave does not have yet: write these yourself, or use a service.
fx-rate-source Where exchange rates come from: money.convert takes a rate you supply; fetching and storing daily rates (ECB, a provider's API) is yours.money-storage Storing amounts: the database columns (integer minor units plus a currency code) and their migrations are yours.time-zones Time zones and daylight saving: caps works in ISO dates, UTC and wall-clock times; converting with the IANA tz rules is yours.locale-formatting Showing dates in a user's language and format ("3 octobre 2026"): caps returns ISO dates, not localised text.non-uk-holidays Public holidays outside the UK: dates.bank-holidays is UK only; pass another country's list to the working-day functions yourself.mtd-submission Making Tax Digital: submitting the return to HMRC's VAT API (OAuth, fraud-prevention headers, obligations) is yours; caps gives the nine boxes.corporation-tax Corporation tax and self-assessment income tax computations are not in caps.vat-number-lookup Checking that a VAT number is registered (HMRC's lookup API) is network work; caps checks the checksum only.