Thermal modernisation tax relief 2026 – how do you claim a tax deduction for mineral wool and how much will you save?

Are you planning to insulate your loft with mineral wool? The cost of the material may be eligible for the thermal modernisation tax relief if you meet the conditions set out in the regulations. Find out how to document your purchase, calculate the savings and claim the relief on your PIT return.

What is the energy-efficiency renovation tax relief and who is eligible for it?

The thermal modernisation tax relief allows taxpayers to deduct from their income – or, in the case of the flat-rate tax on revenue, from their revenue – the expenses incurred on a thermal modernisation project in a detached house. The legal basis for this is Article 26h of the Personal Income Tax Act. The relief has been in force since 2019, and the deduction limit currently stands at PLN 53,000 per taxpayer.

If you’re planning to insulate your loft, it’s worth keeping two matters separate: the technical aspects of the work and the subsequent settlement of expenses. If you’re primarily interested in the former, check out How to insulate your loft, step by step. Here, we focus on the tax aspects of the investment.

Conditions for claiming the relief – a detached house, a PIT taxpayer

The relief is available to the owner or co-owner of a single-family residential building. This also applies to semi-detached and terraced houses, provided they meet the definition of a single-family residential building. The relief does not apply to buildings that are still under construction.

It doesn’t matter whether you carry out the work yourself or use the services of a team. What is important, however, is that the expense incurred is included in the list of deductible expenses and is properly documented.

Taxpayers who settle their income using the tax scale or the flat-rate tax 19% are eligible for the relief. The regulations also allow taxpayers subject to a lump-sum tax on recorded income to deduct their expenses. Depending on the form of taxation, the relief reduces either income or turnover.

The deadline for completing the project is also important. The energy efficiency improvement project should be completed within three years from the end of the tax year in which the first expenditure was incurred. If this deadline is not met, any amounts previously deducted must be added back to income or turnover.

How much is the energy efficiency renovation tax relief in 2026?

The maximum amount of the deduction is 53,000 zł per taxpayer. The limit applies to all energy-efficiency improvement projects carried out by a given person in buildings of which they are the owner or co-owner. It is therefore not a limit applied exclusively to a single purchase of insulation or a single improvement project.

Importantly, 53,000 zł does not automatically mean a tax refund of 53,000 zł. The relief reduces the tax base, i.e. the amount on which the tax is calculated. So, if you spend 10,000 zł, you do not get 10,000 zł back, but you can deduct that amount from your income or revenue.

For example, under the simplified assumption that the entire deduction affects the taxable portion of income at a given rate, an expenditure of 10,000 zł results in the following tax effect:

Rate	Deduction	Estimated benefit
12%	10,000 zł	1,200 zł
19%	10,000 zł	1,900 zł
32%	10,000 zł	3,200 zł

This is a simplification. The actual benefit depends on your tax situation, including your level of income, whether you claim other tax reliefs, and your tax regime. In the case of the tax scale, one cannot assume that all income will be taxed at the 12% or 32% rate.

Is mineral wool eligible for the thermal modernisation tax relief?

Yes, the purchase of mineral wool used for an eligible thermal modernisation project may be eligible for a tax deduction. However, it is important to interpret the current regulations correctly: the regulation does not explicitly list every type of mineral wool. The catalogue does, however, include building materials used for the thermal insulation of building partitions, roofs and foundations, provided they meet the conditions set out in the regulations.

Therefore, when it comes to claiming a tax credit, it is not only the name of the product that counts, but also its use as part of a thermal modernisation project.

Which insulation materials are eligible for the tax relief?

The current catalogue of expenditure is set out in the Regulation of the Minister of Investment and Development of 21 December 2018 on the list of types of building materials, equipment and services relating to the implementation of thermal modernisation projects. The consolidated text of this act was published in 2025.

The current catalogue includes, amongst other things, building materials used for the thermal insulation of building partitions, balcony slabs, roofs and foundations, which form part of thermal insulation systems or are used to protect against damp. This means that mineral wool used as a thermal insulation material as part of such a project may be eligible for tax relief.

When insulating an attic, therefore, the purpose of the purchase and the intended use of the material are important. It is not enough simply to state that you are buying building materials – they must be used for a project that meets the statutory requirements.

Our list may also be helpful when making your choice: Knauf mineral wool – overview and prices.

Mineral wool for the loft – how do you provide proof of purchase?

The most important document is an invoice issued by a VAT-registered trader who does not benefit from a VAT exemption. The Ministry of Finance states explicitly that the right to the relief is evidenced by such an invoice.

There is no requirement to buy wool from a high-street shop. An online purchase may also qualify for the tax relief, provided that all the conditions for the relief are met and you receive a valid invoice.

The invoice should include a description that allows the purchased item to be identified. It is therefore advisable to avoid situations where the document contains only a very general description that makes it difficult to determine what the expenditure was for. In addition, keep your online order, payment confirmation and delivery note. These do not replace the required invoice, but they can help to demonstrate the circumstances of the purchase.

If you’re planning to buy insulation for your loft, you can buy mineral wool with a VAT invoice. When it comes to tax relief, the most important thing is that the document correctly substantiates the expenditure incurred.

It is also worth bearing in mind that, for the purposes of the tax relief, the date on which the invoice is issued is deemed to be the date on which the expenditure was incurred.

How do you work out how much you’ll save on the energy-efficiency renovation tax relief?

The amount of the tax benefit depends on the value of your eligible expenses and your tax circumstances. The simplest way to calculate this is to multiply the amount of the deduction by the rate at which that portion of your income or revenue is taxed. In the actual tax return, however, you must take into account all other elements of the return.

Example: insulating an 80 m² loft with mineral wool – how much of a refund can you get?

Let’s assume you’re insulating an 80 m² loft and buying two layers of mineral wool. For example, let’s assume the approximate cost of the material is between 4,000 and 5,600 zł. On top of this, there are other eligible materials, which cost, for example, between 500 and 800 zł.

The total expenditure used in this example is 4,500–6,400 zł.

With an expenditure of this kind, the approximate tax benefit is as follows:

Amount of expenditure	12%	19%	32%
4,500 zł	540 zł	855 zł	1,440 zł
5,000 zł	600 zł	950 zł	1,600 zł
6,400 PLN	768 zł	1,216 PLN	2,048 zł

These are indicative figures, not a guaranteed „refund” from the tax office. The final amount depends on the individual taxpayer’s tax return.

The prices of building materials vary depending on the manufacturer, specifications, insulation thickness, special offers and transport costs. It is therefore worth checking the current price and the quantity of material required before making a purchase. If you are unsure about the thickness of the insulation, see also 15 cm mineral wool – how much do you need and how much does it cost?.

If you also use eligible services as part of the project, the cost of these services may increase the amount of expenditure covered by the relief. However, the value of your own labour cannot be deducted.

The 53,000 zł tax deduction limit – how can you make the most of it?

Limit 53,000 PLN This applies to all energy efficiency improvement projects carried out by the taxpayer in buildings of which they are the owner or co-owner. This does not mean that each project has a separate limit of 53,000 zł.

If, in any given year, you are unable to claim the full amount due to the level of your income or revenue, the unused portion may be claimed in subsequent years. This period may not exceed six years, counting from the end of the tax year in which the first expenditure was incurred.

In the case of married couples, each spouse is entitled to the allowance separately. However, this does not automatically mean that any amount up to 106,000 PLN can be deducted. The total deduction must correspond to the expenses actually incurred and properly documented, and the method of settlement depends, amongst other things, on the ownership of the property and the spouses’ financial circumstances.

The Ministry of Finance states that, in the case of jointly owned property, spouses may deduct expenses according to the name on the invoice. If the document contains the details of both spouses, they may split the expense in any proportion, but they may not exceed the total amount of the jointly incurred expense or the limit of PLN 53,000 per person.

Step by step – how to claim a tax deduction for mineral wool

The process of claiming the tax relief does not begin only when you fill in your PIT return. The safest approach is to ensure you have the necessary documentation in place whilst you are still planning your investment.

What documents should you gather before buying wool?

First, check whether you are the owner or co-owner of an existing single-family residential property. The property must not be under construction.

Next, specify the scope of the planned thermal modernisation. When insulating your loft, it is worth keeping a record of where the material is to be used and the scope of the work. You do not need to carry out an energy audit solely to claim the tax relief — the Ministry of Finance confirms that an audit prior to the start of the project is not a prerequisite for the deduction.

When making a purchase, ask for a VAT invoice issued by a registered VAT payer. You should also keep your order confirmation, payment receipt and delivery note. However, the most important document remains the invoice, as it serves as the basis for documenting the expense.

Where should I enter the tax relief on my PIT return?

The energy efficiency improvement tax relief is claimed on the PIT return and in the annex PIT/O. This applies, amongst other things, to the PIT-36, PIT-37, PIT-36L and PIT-28 tax returns.

You should include the amount of the eligible deduction in your tax return for the year in which you incurred the expense. If you use the ‘Twój e-PIT’ service, the details of the relief are shown in the relevant tax return, and the PIT/O form is generated as an attachment to the return.

If you buy wool in autumn 2026, you claim the expense on your current 2026 tax return, which you submit at the start of 2027. You do not, therefore, need to wait until the start of the tax year to make the purchase in order to claim the relief – what matters is the year in which the expenditure was incurred, and the date of issue of the invoice is deemed to be the date on which the expenditure was incurred.

When and for how long can you claim the tax relief?

You claim the deduction itself in the year in which the expenditure was incurred. If the amount cannot be offset against your income or revenue for that year, you may carry forward the unused portion to subsequent years, for a maximum of 6 years from the end of the year in which the first expenditure was incurred.

At the same time, the entire project must be completed within three years from the end of the tax year in which the first expenditure was incurred. If this deadline is exceeded, any deductions made previously must be added back to income or turnover.

Example: if you incur your first expenditure in 2026, the three-year period is counted from the end of 2026. This does not, therefore, mean that the investment must be completed exactly three years from the date the first invoice was issued.

FAQ – frequently asked questions about the thermal modernisation tax relief

Is the purchase of mineral wool from an online shop eligible for tax relief?

Yes, an online purchase can be claimed under the thermal modernisation tax relief scheme. The regulations do not make the right to a deduction conditional on whether the materials were purchased online or in a high-street shop. However, it is essential to meet all the conditions for the relief, including providing proper documentation of the expenditure in the form of an invoice issued by a registered VAT trader.

The sales channel alone does not, therefore, determine entitlement to the relief. When shopping online, it is advisable to keep your invoice, order confirmation, payment receipt and delivery note.

Do I need a VAT invoice to claim a tax deduction on wool?

Yes. Entitlement to the relief is evidenced by an invoice issued by a VAT-registered taxpayer who does not benefit from a VAT exemption. The Ministry of Finance also notes that an invoice showing VAT issued by an entity from another EU Member State may be used.

Neither a receipt nor a payment confirmation alone can replace the required invoice. Therefore, when purchasing materials for thermal modernisation, it is advisable to ensure you have the correct sales document straight away.

Can I claim a tax deduction for mineral wool if I install it myself?

Yes, carrying out the work yourself does not preclude a tax deduction for eligible materials. The regulations relate to expenditure incurred on materials, equipment and services listed in the catalogue, rather than to an obligation to commission the work from a professional contractor.

However, this does not mean that the value of one’s own labour can be deducted. Only eligible expenses that have actually been incurred and are properly documented are deductible.