Let-to-Buy vs Consent to Let vs Permission to Let: A Buy-to-Let Landlord's Guide to the Differences

Overview: why these mortgage types matter for landlords

If you’re a landlord planning a move and want to keep your current home, the mortgage route you choose can affect your lender’s requirements, the flexibility you have, and the risk if circumstances change. In the UK, three terms often come up:

• Let-to-Buy mortgages (often a remortgage to buy-to-let while you buy a new main home)
• Permission to Let (a form of consent from your current lender to rent the property temporarily)
• Consent to Let (similar concept to Permission to Let, but wording varies by lender/product)

Although they can look similar on the surface—renting out a property you previously lived in—the underwriting approach and lender expectations are not the same.

Let-to-Buy mortgages: what they are

A Let-to-Buy mortgage is typically used when you are:

1. Keeping your existing property and renting it out, and
2. Buying a new property that will become your main residence
3. Remortgaging the original property onto a buy-to-let basis (or a product designed for this transition)

How lenders usually assess affordability

With Let-to-Buy, the lender’s focus is commonly on rental income and property equity, rather than your employment income in the same way as a standard residential mortgage.

Common underwriting themes include:

• Equity requirements (a deposit/equity buffer is often expected)
• Rental coverage (rental income needs to be sufficient relative to the mortgage payment basis used by the lender)
• Property and rental suitability (including the expected rent and whether the property is appropriate for letting)

Why landlords choose Let-to-Buy

• A longer-term structure compared with temporary permission routes
• Potential to release additional funds to support the purchase of the new home (subject to lender criteria)
• Interest-only options may be available depending on the lender/product

Permission to Let / Consent to Let: what they are

Permission to Let (or Consent to Let) is generally where you ask your current mortgage lender for approval to rent out your home while you live elsewhere temporarily or while you complete a property purchase.

This route is usually considered when you want to:

• Avoid selling your current home immediately
• Keep your existing mortgage product for a period
• Buy a new property without converting the mortgage straight away

How lenders typically manage the permission period

Many lenders treat permission as time-limited and may review it periodically. In practice, this can mean:

• Permission granted for a set period (often around a year, though it varies)
• Reassessment at renewal/review
• Potential changes to pricing (for example, moving to a different rate category)
• Fees for granting or reviewing permission

The key risk: permission can expire

Unlike a buy-to-let conversion, permission is not always open-ended. If the lender’s conditions are not met at review—such as rental performance, equity position, or rental coverage—your options may narrow. That can include being required to sell or convert to a buy-to-let structure.

Let-to-Buy vs Permission/Consent to Let: the practical differences

1) Underwriting focus

• Let-to-Buy: typically assessed on rental income and equity for the remortgage to a buy-to-let basis.
• Permission/Consent: assessed by your existing lender under their policy for allowing a residential mortgage to be let.

2) Time horizon

• Let-to-Buy: usually positioned as a more durable arrangement.
• Permission/Consent: often temporary with review points.

3) What happens if circumstances change

• Let-to-Buy: you’re already operating under a buy-to-let framework.
• Permission/Consent: if permission is not renewed or conditions tighten, you may face a forced change in strategy.

Lender “quirks” and common criteria themes

Buy-to-let and permission routes can involve lender-specific rules. While criteria change over time, the following themes are frequently encountered.

The “track record” issue

Some lenders may require evidence that the property has been let for a period before they will allow a remortgage to a buy-to-let basis.

Other lenders may be more flexible, but this varies by lender and product.

Whether Let-to-Buy borrowing counts as a commitment

Lenders may treat Let-to-Buy borrowing differently when assessing your overall position.

In some cases, rental evidence may be used to support the application; in others, the lender may also want to see that your personal income can support the position until rental history is established.

Criteria are fluid

Mortgage underwriting changes. Even within the same lender, product rules and interpretation can shift. For that reason, it’s important to consider lender criteria as dynamic, not fixed.

Rental income, affordability and rental coverage

For landlords, the practical question is often: Will the lender accept the rental income you’re planning to achieve?

In both Let-to-Buy and buy-to-let conversions, rental coverage usually depends on:

• The expected rent (and how it is evidenced)
• The mortgage payment basis used by the lender (for example, interest-only assumptions)
• The loan-to-value/equity position

Because rental assumptions matter, landlords often need to ensure the rent used in underwriting is realistic and supportable.

Tax considerations for landlords

When you rent out a property, you are generally moving into a landlord position for tax purposes.

Key points to consider:

• You may need to complete an annual tax return.
• You may be able to offset allowable mortgage interest as part of property income calculations, but the treatment of capital and interest differs.
• When you sell, capital gains tax may be relevant, particularly where the property is no longer your main residence.

Tax rules are complex and can change. It’s sensible to consider advice from a qualified tax professional for your specific circumstances.

Insurance considerations

If a property becomes a rental, you typically need to update insurance arrangements.

Common actions include:

• Switching from home insurance to a landlord/let property policy
• Ensuring the policy reflects the property’s occupied status and rental use

Insurance requirements can be a condition of the mortgage and also important for risk management.

Risk management: what landlords should watch

Converting to buy-to-let (or operating under a permission arrangement) introduces risks that are different from a standard residential mortgage.

Ongoing payments regardless of tenancy

Even if the property is temporarily vacant or tenants change, the mortgage payment remains due.

Permission route exposure

With Permission/Consent to Let, the risk is that the lender may require a change if conditions are not met at review.

Operational and compliance factors

Landlords should also consider the wider letting responsibilities that come with renting out a property, including ensuring the property is suitable and properly managed.

Choosing the right route for your timeline

A useful way to decide between Let-to-Buy and Permission/Consent to Let is to consider your intended timescale and your ability to meet lender conditions.

• If you’re aiming for a longer-term rental strategy while buying a new home, Let-to-Buy may align better with that plan.
• If you need a short-to-medium transition and expect to be able to meet the lender’s permission terms at review, Permission/Consent to Let may be considered.

In both cases, the lender’s view of rental income, equity, and evidence requirements will be central.

Important note on advice and regulation

Mortgage and insurance arrangements can be complex, and the tax treatment of property income and gains can be especially technical. This guide is intended to explain the concepts and typical lender approaches at a high level. For legal and tax matters, it’s appropriate to seek advice from a solicitor or accountant.

Summary

• Let-to-Buy mortgages generally involve remortgaging to a buy-to-let basis with underwriting focused on rental income and equity.
• Permission to Let / Consent to Let is lender approval to rent out a residential mortgage property temporarily, usually with review points and potential pricing or conditions changes.
• Lender rules can differ—particularly around rental evidence/track record and how borrowing is assessed.
• Landlords should also factor in tax, insurance, and the practical risk of mortgage payments continuing regardless of tenancy.