Partnership SDLT Relief on Incorporation: FA 2003 Schedule 15, the Sum-of-Lower-Proportions Calculation, and the Three-Year Anti-Withdrawal Trap

Where a genuine partnership transfers its rental portfolio to a connected limited company at incorporation, FA 2003 Schedule 15 can deliver zero SDLT on the entire transfer. The mechanic is the sum-of-lower-proportions (SLP) formula at paragraph 12: chargeable consideration equals market value multiplied by (1 minus SLP%), so a 100% SLP outcome eliminates the SDLT liability that would otherwise hit market value plus the 5% additional-dwellings surcharge under the post-October-2024 regime. The textbook outcome is six-figure SDLT savings on a £1m to £2m portfolio at incorporation, but three load-bearing facts shape every real-world case: partnership share for SLP purposes is income-profit share under paragraph 34 (not capital, not voting, not winding-up assets); the connected-persons test imports CTA 2010 s.1122, which captures spouses, civil partners, lineal ascendants and descendants, siblings, and controlled-company chains, but does NOT capture cohabiting unmarried couples; and the three-year anti-withdrawal rule under paragraph 17A claws the relief back if a partner reduces their partnership share or withdraws capital within 36 months of the transfer. The right HMRC manual reference is SDLTM33500+, not SDLTM09050+ which covers the unrelated section 75A Ramsay general anti-avoidance code.

This page is the operational pillar on the partnership-incorporation SDLT mechanic. The reference scenario is the Mawell-Estate partnership, an anonymised composite: Asha and Diya Mawell, sisters in their late forties, operate a 50/50 general partnership formed in March 2024 holding six rental properties (six BTL flats and a converted Victorian terrace, total market value £1.6m at incorporation, £600,000 aggregate mortgages outstanding). The partnership has filed partnership SA800 returns for tax years 2024/25 and 2025/26, runs a partnership bank account in the partnership name, holds the mortgages jointly, and has been the registered landlord on tenancy agreements throughout. In April 2026 the partnership transfers the portfolio to Mawell Properties Ltd, a new limited company owned 50/50 by Asha and Diya. The SLP calculation produces 100%; the chargeable consideration is £0; the SDLT due is £0; the saving against the no-relief baseline is approximately £170,000 of SDLT (the 5%-surcharged residential rates on £1.6m). This page is the depth-page complement to our SDLT on incorporation overview, our section 162 CGT incorporation relief page, our incorporation holdover relief page, our SDLT sub-sale relief mechanics page, and our LLP for property investment overview.

What Schedule 15 actually does, and when it does not

Schedule 15 is the SDLT relief framework for transactions involving partnerships. It operates in three principal directions. Transfers into a partnership (paragraphs 10 to 13) cover the case where a partner or connected person conveys a chargeable interest into the partnership; the chargeable consideration is reduced by the SLP percentage. Transfers of partnership interests (paragraphs 14 to 17) cover the case where a partner sells their partnership interest to another person, with distinct treatment for property-investment partnerships. Transfers out of a partnership to a partner or connected person (paragraphs 18 to 20) cover the incorporation case where the partnership conveys property to a corporate vehicle controlled by the partners; the SLP calculation operates mirror-symmetrically to the transfer-in formula.

The route delivers zero SDLT only where the SLP calculation reaches 100%. This requires the post-transaction partnership shares (under the para 34 income-profit metric) to align with the pre-transaction beneficial ownership of the chargeable interest, with all relevant partners being connected to one another under CTA 2010 s.1122. The arrangement is statutorily authorised, not a loophole; SDLTM33500 onwards is HMRC's primary operational guidance and was last updated on 20 February 2026 at the time of writing. Schedule 15 has been continuously in force since the SDLT regime replaced stamp duty on land transactions in December 2003.

Where the route does NOT deliver zero SDLT: any case where the partnership is not genuinely pre-existing with operational substance (s.75A Ramsay challenge territory, separate HMRC manual at SDLTM09050+); any case where one or more partners are not connected with each other (the cohabitant exclusion is the most common trap); any case where the partnership-share alignment between income-profit-share and the SLP calculation is poor (mismatched capital and income ratios); and any case where the transfer is to a third-party purchaser rather than to the partnership itself or a person connected with the partners.

Paragraph 10: the transfer-in formula and its mirror at paragraphs 18 to 20

Paragraph 10 of FA 2003 Schedule 15 applies where a partner or person connected with a partner transfers a chargeable interest to the partnership. The chargeable consideration is computed under paragraph 11 (which incorporates paragraph 12) as MV × (1 − SLP), where MV is the market value of the chargeable interest and SLP is the sum of the lower proportions computed under paragraph 12. Paragraph 11 also handles cases where the consideration includes rent (rent reduced by the relevant chargeable proportion).

Paragraph 13 was repealed by Finance Act 2007 (it covered an interim treatment that is now consolidated into paragraphs 10 to 12). Sessions writing on Schedule 15 mechanics should ignore practitioner content that cites paragraph 13 as live text; it has been historical for nearly twenty years.

Paragraph 18 mirrors paragraph 10 for transfers OUT of the partnership to a partner or connected person. The chargeable consideration formula is the same MV × (1 − SLP), with the SLP calculation operating analogously to paragraph 12 but with the partner-and-connected-person test applied to the recipient of the chargeable interest rather than the transferor. For the partnership-incorporation case, where the recipient is a limited company controlled by the partners, paragraph 18 is the operative provision and the SLP analysis pairs the company with the partners as corresponding parties. The Mawell-Estate worked example below uses paragraph 18 mechanics.

The sum-of-lower-proportions: paragraph 12 in five steps

Paragraph 12 sets out the SLP calculation. The five steps are statutory; the apportionment freedom in step three allows tax-side optimisation within statutory limits.

1. Step one: identify the relevant owners. Persons who were entitled to a proportion of the chargeable interest before the transaction AND who, after the transaction, are partners OR are connected with partners under CTA 2010 s.1122. In a sole-trader-into-partnership case, the relevant owner is the sole proprietor; in a partnership-into-NewCo case (paragraph 18), the relevant owner post-transaction is NewCo.
2. Step two: identify the corresponding partners. For each relevant owner, the partners who are that owner or are connected with that owner. In the NewCo case, both Mawell sisters are corresponding partners because each is connected with NewCo via the controlled-company test in s.1122.
3. Step three: apportion the relevant owner's pre-transaction proportion. The free-choice apportionment among the corresponding partners. The partners and the partnership can choose how to apportion within statutory limits; the optimal apportionment for SLP maximisation is the partnership-share-weighted apportionment.
4. Step four: each partner's lower proportion. The lesser of (a) the attributable apportionment from step three and (b) the partner's post-transaction partnership share under paragraph 34 (income-profit share). Where (a) and (b) match exactly, the lower proportion equals each; where they diverge, the lower of the two binds.
5. Step five: sum the lower proportions. Sum across all partners to derive SLP percentage. 100% SLP means full relief; lower percentages mean partial relief; 0% SLP means full SDLT at market value.

The structural implication of step four is that the SLP calculation rewards partnerships where the partners' post-transaction income-profit shares match the apportionment of the relevant owner's pre-transaction proportion. Partnerships set up with mismatched ratios (a sole-proprietor-to-partnership transfer where the sole proprietor takes 70% of the partnership but the apportionment to the partner spouses or family members is only 30%) produce sub-optimal SLP percentages. Partnership planning for an upcoming incorporation should anticipate the SLP arithmetic by aligning income-profit shares with the expected NewCo ownership structure.

Worked example: the Mawell-Estate sisters incorporate to NewCo

Facts. Asha and Diya Mawell, sisters aged 47 and 44, formed a 50/50 general partnership in March 2024 to operate a six-property letting business (five BTL flats across South London plus one converted Victorian terrace in Norwich, total market value £1.6m, aggregate outstanding mortgages £600,000). Partnership SA800 returns filed for tax years 2024/25 and 2025/26; partnership bank account in the partnership name; mortgages held jointly in both sisters' names with the lender notified of the partnership use; tenancy agreements name the partnership; partnership accounting on commercial software with separate capital and current accounts. In April 2026 the partnership transfers the portfolio to Mawell Properties Ltd, a new limited company owned 50/50 by Asha and Diya as ordinary shareholders.

Connected-persons analysis. Asha and Diya are sisters, connected under CTA 2010 s.1122(5) (relatives). Mawell Properties Ltd is connected with each sister because each controls the company jointly with the other under s.1122(2) (controlled-company test). All three parties (Asha, Diya, Mawell Properties Ltd) sit within the s.1122 connected-persons web.

SLP calculation under paragraph 18 (transfer FROM partnership):

• Step one: relevant owner post-transaction. Mawell Properties Ltd. The company holds the chargeable interest after the transfer.
• Step two: corresponding partners. Asha and Diya. Each is connected with Mawell Properties Ltd via the controlled-company test.
• Step three: apportionment of relevant owner's pre-transaction proportion. The partnership held 100% of the chargeable interest pre-transaction. Apportioned 50/50 to Asha and Diya (the optimal allocation matching their respective partnership shares and shareholdings).
• Step four: each partner's lower proportion. For Asha: min(50% step-three apportionment, 50% post-transaction partnership share under para 34) = 50%. For Diya: same, 50%.
• Step five: sum. 50% + 50% = 100% SLP.

Chargeable consideration. £1.6m × (1 − 100%) = £0. SDLT due: £0. The 5% additional-dwellings surcharge would have applied on a non-relief baseline (Mawell Properties Ltd is a company, residential transfer) and would have added roughly £80,000 to the non-relief SDLT bill of approximately £90,000; the total saving is therefore in the region of £170,000.

The £600,000 aggregate mortgages assumed by the company on transfer do not change the SLP calculation. The chargeable consideration formula operates on the gross market value of the chargeable interest; assumed-debt consideration (FA 2003 Schedule 4 paragraph 8) does not modify the SLP outcome under Schedule 15 because Schedule 15's specific formula takes precedence over the general chargeable-consideration rules. The mortgage assumption matters for the company's balance-sheet position but not for the SDLT calculation on transfer.

Paragraph 34: partnership share is income profits, not capital or voting

Paragraph 34(2) of Schedule 15 defines partnership share at any time as the proportion in which the partner is entitled at that time to share in the income profits of the partnership. The metric is specifically income profits, not capital profits, not voting rights, and not entitlement to assets on winding up. The structural implication is that any mismatch between income-profit-share and capital/voting-share in the partnership agreement produces a partnership-share figure for SLP purposes equal to the income-profit figure, regardless of how the partnership is otherwise weighted.

The drift trap. Practitioner content frequently asserts that the partnership share is the "ownership share" or the "capital share" or the "voting share". This is wrong. A partnership agreement structured for non-SDLT purposes (typical for older family partnerships where the founder retained capital but ceded operating income to children to spread the income tax) will produce a partnership share for SLP purposes that may be much lower than the apparent ownership stake. A planned incorporation should therefore include an early review of the partnership agreement against the para 34 metric, and (if needed) a documented restructure to align income-profit-share with the intended NewCo ownership pattern. The restructure itself is a partnership-agreement amendment, not an SDLT event; it does not crystallise any tax charge if it precedes the incorporation transfer.

Connected persons under CTA 2010 s.1122: who counts

CTA 2010 s.1122 defines the connected-persons web for SDLT purposes when imported into Schedule 15. The covered categories are: spouses and civil partners (s.1122(5)(a)); relatives, which includes lineal ascendants and descendants, siblings, and their spouses or civil partners (s.1122(5)(b)); spouses or civil partners of relatives; relatives of spouses or civil partners; trustees of settlements where the settlor or relatives are connected; companies controlled by the same person or persons connected with them.

The strict exclusions matter operationally. Cohabiting unmarried couples are NOT connected under s.1122 regardless of relationship duration; the statute draws the line at formal marriage or civil partnership. Cohabitants intending to use Schedule 15 SLP have three structural options: marry or enter a civil partnership before the partnership-incorporation transfer (changing the s.1122 status); restructure the partnership so other connected family members (a sibling, a parent, a child) hold the partnership shares; or accept that SLP relief is unavailable and either pay the SDLT or pursue alternative mechanisms (none are widely available for the cohabitant case).

Friends-and-business-partners structures sit in the same exclusion territory. Two unrelated business partners running a genuine landlord partnership cannot use Schedule 15 SLP at incorporation; they are not connected under s.1122. The route operates only within family or controlled-company relationships, by statutory design.

Paragraph 17A: the three-year anti-withdrawal trap

The three-year window is the anti-Ramsay safeguard built into Schedule 15. Paragraph 17A applies, verbatim, during the period of three years beginning with the date of the land transfer. A qualifying event during that window triggers a deemed chargeable transaction up to the amount withdrawn, capped at the market value of the originally transferred chargeable interest reduced by any amount already charged.

Qualifying events include: a partner withdrawing capital from the partnership; a partner reducing their partnership interest; a return of capital in any form; repayment of a partner loan to the partnership where the SDLT calculation factored in that loan; the partnership ceasing or being dissolved in a manner that returns capital to the partners.

For the Mawell-Estate scenario, the three-year window runs from April 2026 to April 2029. During that period: neither sister can reduce her 50/50 shareholding in Mawell Properties Ltd in a way that would constitute a capital withdrawal from the underlying partnership-incorporation arrangement; the partnership cannot be formally dissolved in a manner that returns the underlying property value to the partners; partner loan accounts cannot be repaid in a way that constitutes capital withdrawal. After April 2029 the constraint falls away and the sisters can restructure the company shareholding freely (gifts to family members, share-class changes, share buybacks all become available).

The seven-year framing that appears in older practitioner content is incorrect on Schedule 15. The seven-year window is the IHT PET clock and is unconnected with the SDLT-side anti-withdrawal mechanic, which is three years (not seven, not five). Practitioner content quoting seven years has confused regimes; the operative period is the verbatim "period of three years beginning with the date of the land transfer".

The genuine-partnership substance requirement and the s.75A Ramsay attack

Schedule 15 itself contains no statutory minimum period for partnership operation pre-transfer. The substance requirement comes from HMRC's enforcement of the general anti-avoidance code under FA 2003 s.75A (the Ramsay code), administered through the SDLT manual at SDLTM09050+. Where HMRC concludes that a partnership has been constructed shortly before incorporation purely to access Schedule 15 SLP, the s.75A challenge may apply: HMRC ignores the partnership for SDLT purposes and treats the transfer as a direct individual-to-company transaction, recovering full market-value SDLT plus interest and penalties.

The working safe-harbour, applied by specialist property-incorporation advisers and consistent with HMRC's post-Project Blue stance: at least two complete tax years of genuine partnership operation pre-transfer. The two-year benchmark is not statutory but operates as the practical threshold below which HMRC routinely opens enquiries and above which the substance test passes in most cases. Three years gives stronger ground; one year invites enquiry; six months or less invites near-certain challenge.

Five evidence categories carry the substance test in practice. Partnership tax returns under SA800 filed for each completed tax year of operation. Partnership accounting records maintained separately (commercial accounting software preferred over spreadsheets). A partnership bank account in the partnership name with all rental income and partnership expenses flowing through. Joint borrowing on partnership mortgages where the properties are debt-financed. Operational practice (tenancy agreements, contractor invoicing, tenant correspondence) running through the partnership identity. Four or five of these in place for two-plus years substantially reduces the s.75A challenge probability; one or two of them barely registers as substance.

The HMRC manual reference distinction matters. SDLTM33500+ is the partnership-transactions manual, the correct reference for Schedule 15 mechanics under the para 10 / para 18 framework. SDLTM09050+ is the s.75A Ramsay manual, a different territory covering general anti-avoidance. Practitioner content that cites SDLTM09050 for partnership transfers has confused the two manual streams; the structural implication of citing the wrong manual is to conflate statutorily-authorised relief with anti-avoidance enquiry territory, which mischaracterises the legal position of a genuine partnership-incorporation arrangement.

Scottish and Welsh equivalents: LBTT(S)A 2013 Sch 17 and LTTA 2017 Sch 7

Schedule 15 is the SDLT (England and Northern Ireland) framework. Scottish land transactions operate under Schedule 17 of the Land and Buildings Transaction Tax (Scotland) Act 2013; Welsh land transactions operate under Schedule 7 of the Land Transaction Tax and Anti-avoidance of Devolved Taxes (Wales) Act 2017. Both frameworks share architecture with FA 2003 Schedule 15 (an SLP-style formula, an income-profit-share metric for partnership share, a connected-persons web, an anti-withdrawal period) but the procedural detail, the revenue authority administering the filing (Revenue Scotland; Welsh Revenue Authority), and the rate scales applied to any residual chargeable consideration are not identical.

For a cross-border portfolio (English and Scottish properties; English and Welsh properties; or all three jurisdictions), the partnership-incorporation calculation runs three separate analyses under three statutes with three filing requirements. The SLP formula is the same in shape but the jurisdictional context is distinct. Sessions writing on cross-border partnership incorporations must use the right framework for each property and cannot rely on FA 2003 Schedule 15 alone.

Connecting Schedule 15 to the wider incorporation tax stack

Schedule 15 partnership SDLT relief addresses one tax in the incorporation stack. The complete incorporation has three principal tax dimensions, each governed by separate statute. SDLT under FA 2003 (England and Northern Ireland), the focus of this page. CGT under TCGA 1992 ss.162 (incorporation relief, requiring the business to be a trade, which is rare for letting businesses, see our section 162 page) or s.165 (gift holdover, business-asset only, also rare for letting). Corporation tax on the incorporated company at 25% main rate (with marginal relief between £50,000 and £250,000 and small-profits rate of 19% at £50,000 or below).

An incorporating landlord typically prioritises eliminating the SDLT (via Schedule 15 if the partnership route is available) and accepts the CGT exposure on transfer at market value, often supported by the property value not having moved significantly above the base cost or by mortgage interest restriction under s.24 ITA 2007 making the personal-ownership position progressively less attractive year-on-year. Our SDLT on incorporation overview sets the entry-point context; this page is the depth on the Schedule 15 mechanic itself; our incorporation holdover relief page covers the CGT-side options; and our LLP for property investment page covers the intermediate-vehicle option for families on a multi-year run-up to corporate incorporation.