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

If you run your rental business as a genuine partnership and you move the portfolio into a connected limited company at incorporation, FA 2003 Schedule 15 can take the SDLT on the whole transfer down to zero. 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 wipes out the SDLT that would otherwise land on full market value plus the 5% additional-dwellings surcharge under the post-October-2024 regime. On a £1m to £2m portfolio that is six figures of SDLT saved. Three facts decide every real 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 HMRC manual you want is SDLTM33500+, not SDLTM09050+ which covers the unrelated section 75A Ramsay general anti-avoidance code.

The worked example running through this 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). SDLT is only one tax in the incorporation. For the full picture sit this alongside the SDLT on incorporation overview, the section 162 CGT incorporation relief, incorporation holdover relief, the SDLT sub-sale relief mechanics, and, if you are years away from a corporate move, the LLP for property investment route.

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.

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

It does NOT get you to zero in four situations: where the partnership is not genuinely pre-existing with operational substance (s.75A Ramsay challenge territory, separate HMRC manual at SDLTM09050+); where one or more partners are not connected with each other (the cohabitant exclusion is the most common trap); where the alignment between income-profit-share and the SLP calculation is poor (mismatched capital and income ratios); and where the transfer goes 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 now consolidated into paragraphs 10 to 12). If you see older practitioner content citing paragraph 13 as live text, ignore it; 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 whoever receives the chargeable interest rather than to whoever transfers it out. For your partnership-incorporation, where a limited company controlled by the partners takes the property, paragraph 18 is the operative provision and the SLP analysis pairs the company with the partners as corresponding parties. The Mawell-Estate worked example runs on 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.

Step four is where the calculation rewards you for matching the partners' post-transaction income-profit shares to the apportionment of the relevant owner's pre-transaction proportion. Mismatched ratios cost relief: take a sole-proprietor-to-partnership transfer where the sole proprietor keeps 70% of the partnership but the apportionment to the partner spouses or family members is only 30%, and the SLP percentage falls short. If you are heading for incorporation, plan the SLP arithmetic in advance and align your income-profit shares with the company ownership structure you intend to put in place.

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 your 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. That is income profits, full stop: not capital profits, not voting rights, not entitlement to assets on winding up. So any mismatch between income-profit-share and capital or voting share in your partnership agreement gives you a partnership-share figure for SLP purposes equal to the income-profit figure, however the partnership is otherwise weighted.

This is where people come unstuck. You will see the partnership share described as the "ownership share" or the "capital share" or the "voting share". It is none of those. A partnership agreement drawn up for non-SDLT reasons (common in older family partnerships, where the founder kept the capital but passed operating income to the children to spread the income tax) can hand you a partnership share for SLP purposes well below your apparent ownership stake. Before you incorporate, read your partnership agreement against the para 34 metric, and if it does not match the company ownership pattern you want, restructure it and document the change. That restructure is a partnership-agreement amendment, not an SDLT event; it crystallises no tax charge as long as 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 exclusions are where the relief is won or lost. Cohabiting unmarried couples are NOT connected under s.1122, however long you have been together; the statute draws the line at formal marriage or civil partnership. If you and your partner cohabit, you have three options: marry or enter a civil partnership before the transfer (which changes your 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 off the table and either pay the SDLT or look at alternative mechanisms (and for cohabitants, none are widely available).

The same exclusion catches friends and unrelated business partners. If you run a genuine landlord partnership with someone you are not related to, you cannot use Schedule 15 SLP at incorporation, because you are not connected under s.1122. The route works 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).

Ignore the seven-year framing you may have read elsewhere. The seven-year window is the IHT PET clock and has nothing to do with the SDLT anti-withdrawal mechanic, which is three years (not seven, not five). Older content quoting seven years has muddled the two 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 sets no statutory minimum period for how long the partnership must have operated before the transfer. The pressure comes from HMRC's general anti-avoidance code under FA 2003 s.75A (the Ramsay code), administered through the SDLT manual at SDLTM09050+. If HMRC decides your partnership was put together shortly before incorporation purely to reach Schedule 15 SLP, s.75A lets it ignore the partnership for SDLT purposes and treat the move as a direct transfer from you to your company, clawing back full market-value SDLT plus interest and penalties.

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

Five kinds of evidence carry the substance test in practice. Partnership tax returns under SA800 filed for each completed tax year of operation. Partnership accounting records kept separately (commercial accounting software beats spreadsheets here). A partnership bank account in the partnership name, with all rental income and partnership expenses flowing through it. Joint borrowing on partnership mortgages where the properties are debt-financed. And operational practice (tenancy agreements, contractor invoicing, tenant correspondence) running through the partnership identity. Get four or five of these in place for two-plus years and your s.75A challenge risk drops sharply; one or two of them barely registers as substance.

Get the manual reference right too. 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. Content that cites SDLTM09050 for partnership transfers has crossed the two streams, and citing the wrong manual conflates statutorily-authorised relief with anti-avoidance enquiry territory, which misstates the legal position of a genuine partnership-incorporation.

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.

If your portfolio crosses borders (English and Scottish properties, English and Welsh properties, or all three jurisdictions), your partnership-incorporation calculation runs three separate analyses under three statutes with three filing requirements. The SLP formula is the same in shape, but the jurisdiction changes the detail. Use the right framework for each property; you cannot rely on FA 2003 Schedule 15 alone.

How does Schedule 15 fit the rest of your incorporation tax bill?

Schedule 15 only deals with one tax. Incorporation has three principal tax dimensions, each under its own statute. SDLT under FA 2003 (England and Northern Ireland), which is what you have just worked through. CGT under TCGA 1992 ss.162 (incorporation relief, which needs the business to be a trade, rare for letting businesses, covered in our section 162 guide) or s.165 (gift holdover, business-asset only, also rare for letting). And corporation tax on the company itself at the 25% main rate (with marginal relief between £50,000 and £250,000 and a small-profits rate of 19% at £50,000 or below).

Most landlords incorporating prioritise killing the SDLT (via Schedule 15 where the partnership route is open) and accept the CGT exposure on transfer at market value, often because the property value has not moved far above base cost, or because the s.24 ITA 2007 mortgage interest restriction makes holding personally less attractive every year. To see the whole sequence, the SDLT on incorporation overview sets the entry-point context, your CGT-side options sit in the incorporation holdover relief guide, and if you are on a multi-year run-up to a company, the LLP for property investment guide covers the intermediate vehicle.