Give sharers, boarders and lodgers their own rent, tenure and LHA category

[MaxGhenis]

Fixes #2005

Stacked on #1896 (base remove-is-child-flags), which adds is_claimant_or_partner, lha_renter_has_non_dependant and the specified-renter test that this builds on. The data comes from PolicyEngine/policyengine-uk-data (companion PR to follow).

Summary

Families other than the household head's had no rent. This gives them the treatment the regulations set out:

• Sharers. Joint tenants and other sharers of a household's rent are each liable for a per-person share of it.
• Boarders and lodgers are liable for what they pay the householder, and they rent privately whatever the household's tenure.
• Non-dependants. Families liable for rent are not non-dependants of anyone, and only the household head's family has non-dependants from other families.
• HB LHA category. Housing Benefit gets its own LHA category and size criteria next to Universal Credit's.
• HB meals. Meals in the rent come off Housing Benefit eligible rent.
• CTR. Council Tax Reduction divides the council tax among jointly liable sharers.

The law (read for this PR; texts and an independent legal memo in the review folder)

Rent liability

• UC. A licence or other permission to occupy is a rent payment (UC Regs 2013 Sch 1 para 2(b)).
• UC, sharers. Where several people are liable for the same rent, the renter's core rent is A/B × C: the total ÷ all persons liable × listed persons liable (Sch 4 para 24(4)).
• HB. A licence is rent (HB Regs 2006 reg 12(1)). Shared rent is apportioned having regard to the number of persons and the proportion each pays (reg 12B(4)).

Tenure

• UC Part 4 (private rented) applies to renters liable to anyone other than a social landlord (Sch 4 para 20). A lodger of a council tenant is therefore a private renter.
• For HB this is a rent allowance with the LHA (reg 13C; SSAA 1992 s. 134).

Non-dependants

• UC. None of these is a non-dependant (Sch 4 para 9(2)(d)-(f)):
  • a person liable on a commercial basis "whether to the renter, joint renters or another person";
  • the person to whom the renter's liability is owed, or a member of their household;
  • anyone already counted in another claim for the same accommodation.
• HB.
  • Joint occupiers and commercial occupiers are excluded (reg 3(2)(d)-(e)). Sharers liable separately to the landlord do not "reside with" each other (reg 3(4)).
  • A non-dependant of several joint occupiers is apportioned between them (reg 74(5); SPC reg 55(5)).
• CTR. People jointly and severally liable for the council tax, and commercial occupiers, are excluded (SI 2012/2885 reg 9(2)(d)-(e)). A shared non-dependant is apportioned equally (Sch 1 para 8(5)).

LHA category

• UC. The cap rent is the LHA for the category the renter is entitled to (Sch 4 para 25(2)(b); paras 8-12, 26-29). Only a "specified renter" (single, under 35, not excepted, no child, no non-dependant) is limited to shared accommodation (paras 27-28). A single renter aged 35 or over in a room gets the one-bedroom rate.

• HB. The shared rate applies (reg 13D(2)) to:

  • a young individual with no non-dependant;
  • anyone entitled to one bedroom who lacks exclusive use of two rooms, or of a room with a bathroom, toilet and kitchen.

  Either way it does not apply where the severe disability premium applies. In the exclusive-use test, rooms shared with the claimant's household, non-dependants or people paying the claimant rent still count as exclusive.

• HB size criteria count every "occupier" except a joint tenant outside the claimant's household (13D(3), (12)). So a householder's lodger adds an HB bedroom but not a UC one.

Meals

• UC. The food exclusion in service charges applies only in the social sector and to owner-occupiers (Sch 1 para 8(1), (6)(c); ADM F2060). A private boarder's whole payment is core rent, capped at the LHA.
• HB. On the LHA route the cap rent is gross. Where a rent officer finds that a substantial part of the rent is board and attendance, the case leaves the LHA (reg 13C(5)(e), 13D(10)). The fixed Sch 1 para 2 amount for meals is then deducted from the maximum rent (reg 13(7) as substituted by SI 2007/2868).

CTR, joint liability. The maximum reduction uses the council tax divided by the number of persons jointly and severally liable, with no division where the only other liable person is the partner (England pensioners SI 2012/2885 Sch 1 para 7(3)-(4); Wales SI 2013/3029 Sch 1 para 2, Sch 6 para 4; Scotland SSI 2021/249 reg 79).

What changed

Rent liability. benunit_rent and the new share_of_household_rent hold each family's own liability. personal_rent puts the family's share on the household head (head's family) or the family head (others), so the household head still carries the whole rent where no one else is liable. The family's liability is:

• the household's rent per person liable, across the household head's family and any family with the new input liable_for_share_of_household_rent;
• plus rent_paid_as_boarder and rent_paid_as_lodger.

Those two inputs and pays_rent_to_householder are byte-identical copies of #2002's files at the same paths, so the two PRs merge in either order.

Tenure. benunit_tenure_type is the family's own tenure: a boarder or lodger rents privately. in_social_housing and uc_housing_costs_element follow it.

Non-dependants

• New is_non_dependant_of_household_head.
• UC deductions, UC bedrooms and lha_renter_has_non_dependant count non-dependants for the household head's family only, never families liable for rent.
• HB deductions are apportioned by share of rent.

LHA

• LHA_category (UC) is set by entitlement only; is_shared_accommodation no longer affects it.
• New housing_benefit_LHA_allowed_bedrooms, housing_benefit_shares_accommodation, is_housing_benefit_young_individual, housing_benefit_LHA_category and housing_benefit_LHA_rate.
• LHA_cap (HB) uses the HB rate.
• lha_rate_for_category and category_maximum take the category variable.

Meals. New input meals_included_in_rent (default none), parameters gov.dwp.housing_benefit.ineligible_charges.meals.* (dated 2008-2026 from legislation.gov.uk point-in-time texts and each up-rating order), and housing_benefit_meals_deduction. These are applied in LHA_cap and on the non-LHA HB path. The FRS does not record meals, so the dataset leaves this at none.

CTR

• New council_tax_reduction_claimant_benunit: every jointly liable family where the rent is shared; otherwise the old age rule.
• New council_tax_reduction_joint_liability_share.
• Applied in the national schemes and the five local schemes.
• Joint tenants and lodgers are excluded from CTR non-dependants.

Behaviour change for API users

• BRMA_LHA_rate stays the published rate for LHA_category. Housing Benefit now reads housing_benefit_LHA_rate, so an input set on BRMA_LHA_rate no longer drives HB.
• is_shared_accommodation now affects only HB.

Choices where the law leaves room (each documented on the variable)

1. Sharers' split: per person liable, the UC para 24(4) default. HB reg 12B(4) and UC 24(5) allow departures for the actual proportions. In the FRS, HHRENT is about n/(n−1) × the other units' SRENTAMT (median 1.5; 2.0 with two units), which is consistent with equal shares.
2. CTR, couple sharing with others. The regulations' wording divides by every person liable, the partner included, so a couple with one other sharer gets a third. An IFS commentary on the old Council Tax Benefit (C123, 2012) said two-thirds, citing nothing. No DWP or MHCLG guidance was found. Excluded students are not removed from the count.
3. UC: one claim per non-dependant. A non-dependant counts in one UC claim only (para 9(2)(f)); the model gives it to the household head's family.
4. HB meals. The rent officer route is modelled as rent less the meals amount, capped at the HB LHA rate, which stands in for the rent officer's figure.
5. Not modelled:
   • care-leaver, hostel, MAPPA, domestic-abuse and modern-slavery exceptions;
   • foster children;
   • social-sector size criteria (bedroom tax), which the model applies to no one;
   • close relatives paying commercial rent (the FRS asks CVPAY only of people unrelated to the HRP);
   • for a sharer's own CTR claim, the household-level pensioner-scheme test and non-dependant exemption still read the household head's family (follow-up chip from Give Council Tax Reduction to the household head's family, not the oldest adult's #2009).

Invariants and tests

Property tests (Hypothesis) in test_rent_of_sharers_boarders_and_lodgers_properties.py, over generated multi-family households:

1. Conservation: shares of household rent sum to 1, and families' rents sum to household rent plus boarder and lodger payments.
2. Bounds: shares in [0, 1]; rents ≥ 0; non-liable families have no rent.
3. Tenure: a boarder's or lodger's family rents privately, is never in social housing and is LHA-eligible.
4. Non-dependants: liable families are never non-dependants; only the head's family has UC deductions; boarders and lodgers have no HB or CTR deductions.
5. Category: the UC category is invariant to is_shared_accommodation; the HB category is A whenever a family is entitled to one bedroom, lacks exclusive use and has no SDP.
6. Meals: deduction ≥ 0, and meals never raise HB eligible rent.
7. CTR: claim shares in a shared household total ≤ 1.
8. Monotonicity in household rent.
9. No-op: without sharers, boarders or lodgers, rent and the head's UC deductions equal the previous formulas.

YAML tests, with the arithmetic in comments:

• rent_of_sharers_boarders_and_lodgers.yaml
• housing_benefit/housing_benefit_meals_deduction.yaml
• council_tax_reduction/joint_liability.yaml

Updated tests whose expectations encoded the old proxies:

• UC and HB non-dependant aggregation;
• four LHA_claimant_composition cases;
• the pension-age HB LHA case.

Results

• Full policy YAML suite: 1,500 passed.
• Full Python suite at b065a48: 2,042 passed, 45 skipped, 0 failed. This includes the six property tests and test_deterministic_variables.

Found while testing and fixed in PRs stacked on this one:

• Give Council Tax Reduction to the household head's family, not the oldest adult's #2009: benunit_contains_household_head gave CTR to two families when their oldest adults were the same age.
• Give benefit-unit members aged 16 or over a bedroom in the LHA size criteria #2010: LHA bedrooms omitted a room for a qualifying young person.

Impact (real microsimulation runs, head 01d140e)

All runs compare this PR's head (01d140e) with its base (143cc3c, #1896) on the same dataset and weights, for 2025-26 and 2026-27. Survey households are counted by a fingerprint of household rent and members' ages, which joins the enhanced FRS copies; any cell behind fewer than 10 is suppressed.

1. Today's published enhanced FRS (snapshot ace89433, sha256 03fe15e40a4c). It has neither the sharer flag nor the boarder and lodger inputs, so this is what the PR does if it merges alone.

• Universal Credit, Council Tax Reduction and Pension Credit awards: no change in either year.
• Housing Benefit: changes in fewer than 10 survey households (suppressed).
• The potential UC housing costs element is computed for every renting family, claimant or not. It moves −£130m (2025-26) because a non-dependant now counts only in a UC claim that is made (Sch 4 para 9(2)(f)). No award moves.

2. Enhanced FRS built from policyengine-uk-data#512 (a9e3371, sha256 ed1a29912656; stacked on #506 and #503, so it carries the sharer flag and the boarder and lodger inputs).

£ a year	2025-26	2026-27
Universal Credit (all families)	+£31.3m	+£34.0m
UC housing costs element, sharers (91 survey households)	£0 → £665m	£0 → £674m
UC housing costs element, boarders and lodgers (36 survey households)	£0 → £147m	£0 → £147m
UC award, sharers	+£72.9m	+£74.5m
UC award, household heads	−£50.3m	−£49.2m
Housing Benefit	<10 survey households (suppressed)	<10 (suppressed)
Council Tax Reduction, Pension Credit	no change	no change

Against calibration targets (build 2)

• UC 2025-26: OBR £79.29bn. Base −4.35%, this PR −4.31%.
• UC 2026-27: OBR £87.65bn. Base −8.73%, this PR −8.69%.
• HB: unchanged against the OBR figure.

The weights were calibrated with policyengine-uk 2.93.0, so these figures hold weights fixed and isolate the rule change.

Methodology readings for Max (d836)

• The per-person split of shared rent.
• The CTR one-third for a couple jointly liable with one other person.

Review

• Round 1 (independent, at b065a48): REQUEST_CHANGES with nine findings, three of them blockers. All are addressed in 01d140e.
  • Findings 7 (QYP bedroom) and the inherited CTR claimant issues are fixed in the stacked Give benefit-unit members aged 16 or over a bedroom in the LHA size criteria #2010 and Give Council Tax Reduction to the household head's family, not the oldest adult's #2009.
• Round 2 (independent, at 01d140e): pending.

axiom: uk/regulations/uksi/2013/376/schedule/4/paragraph/24 encoded-correct (test listed_and_other_persons_are_apportioned_by_formula); TheAxiomFoundation/rulespec-uk#406 queued (UC Sch 4 paras 9 and 20; HB regs 3, 12B, 13(7), 13D, 74(5) and Sch 1 para 2; CTR reg 9 and Sch 1 paras 7-8)

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