Transferring a Buy-to-Let to Your Spouse: CGT, SDLT and Income Tax

Tax 1: CGT — genuinely no charge (but not forgotten)

Transfers between spouses or civil partners who are living together take place at “no gain, no loss” under section 58 TCGA 1992. It doesn’t matter that the flat you bought for £150,000 is now worth £300,000 — the transfer itself produces a gain of exactly zero, and there’s no 60-day CGT return to file.

The catch is that the gain is deferred, not erased. Your spouse takes over your original £150,000 base cost, so when they eventually sell, the whole gain from your purchase date is taxed on them — at 18% or 24% with a £3,000 annual exempt amount. Used well, that’s the point: splitting ownership before a sale means two annual exempt amounts and potentially more of the gain taxed at 18% instead of 24%.

Tax 2: SDLT — the mortgage trap

Here’s where the “tax-free” assumption breaks. SDLT has no general spouse exemption. It taxes chargeable consideration — and if your spouse takes on responsibility for a share of the mortgage, HMRC treats that assumed debt as the price paid.

• No mortgage, no cash changing hands: consideration is nil, so no SDLT and usually no return.
• Mortgaged property: the share of debt your spouse assumes (plus any cash paid) is consideration. Over the £125,000 nil-rate threshold, SDLT is due at standard rates.
• The good news: since 22 November 2017, the additional-property surcharge (now 5%) is disregarded for transfers between spouses living together — even if you own ten other buy-to-lets — provided no third party is involved.

So transferring half a property with a £340,000 mortgage means your spouse assumes £170,000 of debt: that’s £45,000 over the threshold, and SDLT is due at standard rates on the excess — but with no 5% surcharge. Many couples deliberately transfer a smaller beneficial share so the assumed debt stays under £125,000 and the SDLT bill is nil.

Tax 3: income tax — the split only moves with paperwork

This is the step most DIY transfers miss. Once a property is jointly owned by spouses, HMRC taxes the rent 50/50 by default — regardless of the actual ownership shares. If you want the split taxed as, say, 99/1 in favour of the lower earner, you need both:

• A declaration of trust establishing genuinely unequal beneficial ownership; and
• Form 17, filed with HMRC within 60 days of the declaration being signed, with evidence attached.

Miss the 60-day window and you stay on 50/50 until you re-do the paperwork. And Form 17 must follow the real beneficial split — you can’t own 50/50 and elect to be taxed 90/10. We cover the mechanics in detail in our Form 17 guide.

One more angle: if the transfer takes the lower-earning spouse’s gross property income over £30,000 from April 2027 (or £50,000 now), they’ll fall into Making Tax Digital with quarterly updates of their own — worth knowing before you sign.

A worked example: the £2,364-a-year marriage dividend

Sam earns £70,000 (40% band, rising to 42% on property income from April 2027) and owns a buy-to-let making £12,000 taxable profit. His wife Priya earns £18,000 (basic rate). Sam transfers the property into joint names with a declaration of trust giving Priya 99%, and files Form 17. The mortgage is £110,000, so the half assumed is well under the SDLT threshold — nil SDLT.

From April 2027 the same numbers save even more, because Sam’s marginal rate on property income rises to 42% while Priya’s goes to 22%. The one-off cost is conveyancing and the declaration of trust — typically a few hundred pounds — against a saving that repeats every year.

When a spouse transfer is a bad idea

• Separation on the horizon: no-gain/no-loss and the SDLT higher-rates disregard both require you to be living together. Gifts made as a marriage breaks down have their own (recently improved but different) rules.
• Large mortgage: if the assumed debt share exceeds £125,000, SDLT at standard rates may wipe out years of income tax savings. Transfer a smaller share, or get the lender’s consent structure reviewed first.
• Lender consent: adding someone to a mortgaged title without the lender’s agreement breaches the mortgage terms. Always involve the lender — some charge fees or reprice.
• Benefit or student-finance thresholds: shifting income onto a spouse can affect their child benefit taper, personal allowance taper or means-tested entitlements.

Frequently asked questions