Claiming the R&D relief retroactively: how to recover overpaid tax through a correction?

Can the R&D relief be claimed for previous years?

Yes, provided that the given year is not yet time-barred and the company already met the conditions for the relief at that time. A correction does not create a right to the relief “after the fact”. It only amends an earlier settlement in which the taxpayer was entitled to the deduction but did not use it.

The basis for the deduction is Art. 18d of the CIT Act and, for PIT taxpayers, Art. 26e of the PIT Act. The right to amend a previously filed return, in turn, follows from Art. 81 of the Tax Ordinance Act. In practice, this means filing a corrected CIT-8 return together with the CIT/BR attachment, or a corrected version of the relevant PIT return, for example PIT-36 or PIT-36L, together with the PIT/BR attachment.

The most important thing, however, is that the company can show that its historical projects were in fact research and development activity within the meaning of the law. This means creative activity comprising scientific research or development work, carried out systematically and aimed at increasing the stock of knowledge or using knowledge to create new applications. For CIT, this follows from Art. 4a(26) to (28) of the CIT Act, and for PIT, from Art. 5a(38) to (40) of the PIT Act. A decision taken today that “we want to use the relief” is not enough if there are no real projects from the given year behind the deduction.

There are also two limitations that are easy to forget when the topic is presented from a sales perspective.

First, a qualifying cost may not have been reimbursed to the taxpayer in any form or previously deducted from the income tax base. This follows from Art. 18d(5) of the CIT Act and Art. 26e(5) of the PIT Act. So if the company received a grant, a reimbursement or other funding covering part of the project costs, the reimbursed part should, as a rule, not be included in the R&D relief.

Second, companies using special economic zone exemptions or support decisions under the Polish Investment Zone may include in the R&D relief only those costs that were not taken into account when calculating tax-exempt income. This follows from Art. 18d(6) of the CIT Act. Operating in a special economic zone (SEZ) or the Polish Investment Zone (PIZ) therefore does not in itself exclude the R&D relief, but it requires a very precise separation of the costs of taxable and exempt activity.

How many years back can the R&D relief deduction be claimed?

The slogan “5 years back” is convenient, but not entirely precise. The five years are not counted from the date the correction is filed. What matters is when the tax liability for the given year becomes time-barred.

Under Art. 70 § 1 of the Tax Ordinance Act, a tax liability becomes time-barred after five years, counted from the end of the calendar year in which the tax payment deadline fell. This means that we look not only at the year to which the correction relates, but also at the year in which the tax payment deadline fell.

In other words, in September 2026, with a standard tax year, a correction for 2020 and 2021 can still be analysed, but 2020 must be closed before the end of 2026.

Therefore, the safe sentence for the article is: the years that are not yet time-barred can be corrected. Which year is still open depends on the tax payment deadline for a specific year, and in the case of a non-standard tax year or special events, this must be checked separately.

It must also be remembered that the limitation period may be suspended or interrupted. For example, Art. 70 § 6(1) of the Tax Ordinance Act provides for the suspension of the limitation period in connection with the initiation of proceedings concerning a fiscal offence or a fiscal petty offence, if the taxpayer has been notified of this in accordance with the Tax Ordinance Act. In practice, this means that “five years” does not always work like a simple countdown.

There is one more important point: correcting the return alone is not enough if the company wants to recover overpaid tax. An application for a determination of overpayment must also be filed before the limitation period expires. This follows from Art. 79 § 2 of the Tax Ordinance Act. If the taxpayer files the application too late, even a substantively correct correction may not translate into a refund.

What does the procedure for correcting a CIT/PIT tax return look like?

In practice, there are two stages: first, the right to the relief must be reconstructed and documented, and only then are the correction and the application for a determination of overpayment filed. Most of the work usually lies not in correcting the form itself, but in preparing material that will show the tax office that the deduction is justified.

Preparing retrospective records of R&D projects and costs

The law requires R&D costs to be separately identified in the taxpayer’s records. For CIT, this follows from Art. 9(1b) of the CIT Act, and for PIT, from Art. 24a(1b) of the PIT Act. However, there is no single statutory template for the documentation. The law does not impose a specific form of records.

In practice, auxiliary records, for example a spreadsheet, may be sufficient if they make it possible to trace the deduction amount unambiguously back to the source documents. They should show which costs, in which year, in which category and for which project were treated as qualifying costs.

Greater caution is needed when a company wants to reconstruct its records after several years. For taxpayers keeping a tax book of revenue and expenses (PKPiR), there are favourable interpretations on completing column 16 of the PKPiR by way of correction. In interpretation 0115-KDIT3.4011.120.2026.2.PS, the authority held that entering R&D costs in column 16 of the book, in the form of PKPiR corrections for the relevant periods, meets the record-keeping conditions required to use the R&D relief. Similarly, interpretation 0115-KDIT3.4011.831.2024.2.PS concerned corrections for 2019 to 2023.

However, this should not be turned into too broad a rule. These interpretations are an important argument, but they do not mean that every table prepared years later will be accepted. The safe thesis is this: the records can be reconstructed, but they must be based on real data from the period in which the project was carried out. The authority will check whether the costs can be linked to source documents, the team’s work and the actual course of the project, not just to the final refund amount.

This risk is well illustrated by the non-final judgment of the Provincial Administrative Court in Łódź of 17 June 2025 (I SA/Łd 208/25). The company presented project sheets, working time records, payroll documentation and cost summaries, but the court accepted the authority’s assessment that some of the documents may have been created only for the purposes of the overpayment application. The problems included, among others, missing dates, authors and signatures. The conclusion for taxpayers is practical: documentation prepared after the fact must be based on traces from the given year, such as schedules, technical documentation, repositories, project correspondence, test reports, working time records, payrolls, invoices and accounting entries.

Good R&D records should therefore not be just a table of costs. They should answer several questions: what the purpose of the project was, what the creative element consisted of, what the technical or technological uncertainty was, who took part in the work, which costs were allocated to the project, and how the proportion of involvement in R&D was calculated.

Employee costs and deduction limits

In many companies, personnel costs make up the largest part of the R&D relief. Art. 18d(2)(1) of the CIT Act and Art. 26e(2)(1) of the PIT Act allow employees’ remuneration and contributions financed by the payer to be included in the proportion that the time spent on R&D activity bears to the employee’s total working time in a given month. Similar rules apply to remuneration under contracts of mandate and contracts for specific work, under Art. 18d(2)(1a) of the CIT Act and Art. 26e(2)(1a) of the PIT Act.

For corrections for earlier years, however, the limits in force in the corrected year must be applied. This is important, because a correction for 2020 or 2021 cannot automatically use limits that came into force later.

The general interpretation of the Minister of Finance of 13 February 2024 (DD8.8203.1.2021) confirms a favourable approach to remuneration for periods of justified absence. Remuneration for holidays, sick leave or other justified absences may be included in qualifying costs in the appropriate proportion, provided that the other conditions of the relief are met.

Case law on management staff is also favourable for taxpayers. The judgment of the Supreme Administrative Court of 21 March 2023 (II FSK 2217/20) confirms that the remuneration of persons performing managerial or supervisory functions cannot automatically be excluded from qualifying costs if they actually participate in R&D activity or supervise R&D work. What counts is the actual scope of duties, not the job title itself.

In turn, the judgment of the Supreme Administrative Court of 21 November 2024 (II FSK 226/22) is important for bonuses and awards paid for periods longer than one month. It shows that the calculation must take into account not only the payment itself, but also the way the proportion of involvement in R&D is determined. For larger corrections for previous years, personnel costs therefore often require a separate, detailed calculation.

Filing an application for a determination of tax overpayment with the tax office

If the correction reduces the tax due, the taxpayer should file an application for a determination of overpayment. The basis is Art. 75 of the Tax Ordinance Act. Under Art. 75 § 3 of the Tax Ordinance Act, where the taxpayer was required to file a tax return or declaration, the corrected return is filed together with the application for a determination of overpayment.

In practice, the full set of documents should include: the corrected CIT-8 or relevant PIT return, the CIT/BR or PIT/BR attachment, the application for a determination of overpayment, and a justification showing why the relief was available in the corrected year. The justification itself is not always formally required for every correction, but it is very much needed for the R&D relief and an overpayment refund application. Without it, the tax office will probably ask for additional explanations.

The refund deadline must be described with caution. Art. 77 § 1(6)(a) of the Tax Ordinance Act provides for the refund of an overpayment within two months of the date of filing the application together with the corrected return, but not earlier than three months from the date of filing the original return or declaration. This is a good argument for the slogan “a quick cash injection”, but it is not a guarantee of payment in every case.

If the correction raises doubts, the authority may conduct overpayment proceedings, request documents and issue a decision. In such a situation, the refund may come later, and if the authority is late, interest on the overpayment under Art. 78 of the Tax Ordinance Act may be relevant.

Art. 76 of the Tax Ordinance Act must also be remembered. An overpayment does not always go directly to the taxpayer’s bank account. It is first offset ex officio against tax arrears, interest, reminder costs and current tax liabilities. Only if there are no such amounts due does the tax office refund the money to the taxpayer. In practice, “hard cash” may therefore mean either a bank transfer or a reduction of existing liabilities to the tax authorities.

Does a return correction with the R&D relief automatically trigger a tax audit?

No. There is no provision requiring an audit to be initiated merely because the taxpayer has filed a correction with the R&D relief. This is important, because many entrepreneurs fear that simply applying for an overpayment will automatically “bring on an audit”.

This does not mean, however, that the tax office will not ask questions. With a correction for previous years and an overpayment refund application, taxpayers must expect verification activities or overpayment proceedings. Art. 272 of the Tax Ordinance Act allows the authorities to check the timeliness of filing returns, the formal correctness of documents, and to establish the facts to the extent necessary to confirm consistency with the documents presented. Art. 274a § 2 of the Tax Ordinance Act allows the authority to request explanations from the taxpayer if it has doubts about the correctness of the return.

In practice, the tax office’s questions usually concern which projects were treated as R&D, who worked on them, how working time was calculated, which costs were included as qualifying costs, whether the costs were reimbursed to the taxpayer, and whether the amounts in CIT/BR or PIT/BR follow from the books. The older the year and the higher the overpayment amount, the more important consistent documentation becomes.

Art. 79 § 1 of the Tax Ordinance Act must also be taken into account. Proceedings for a determination of overpayment cannot be initiated while tax proceedings, a tax audit or a customs and tax audit are in progress with respect to the same tax liabilities. So if the company is already being audited for a given year and the same scope, the simple path of a correction with an overpayment application may be temporarily unavailable. At the same time, Art. 81b of the Tax Ordinance Act provides for the suspension of the right to correct for the duration of tax proceedings or a tax audit in the scope covered by those proceedings or that audit.

When does a retroactive settlement pay off? Case study and financial benefits

Claiming the R&D relief retroactively pays off when the company actually carried out R&D projects, incurred qualifying costs, had income that allowed the deduction to be used, and paid tax that turns out to be overstated after the correction. In that case, the correction may translate into an overpayment and, after its verification, into a refund or an offset against liabilities.

Example: a company subject to CIT at the 19% rate identifies PLN 1 million of qualifying costs deductible at 100%. The potential tax benefit is approximately PLN 190,000. If these are employee costs incurred in a year in which the 200% limit applies, the deduction amount may increase to PLN 2 million, and the tax benefit to approximately PLN 380,000. This is, of course, an example based on simple figures, not a promise of a specific refund.

For CIT taxpayers using the 9% rate, the effect will be lower, because the R&D relief reduces the tax base, not the tax itself independently of the rate. For PIT taxpayers, the effect depends on the form of taxation, i.e. the progressive tax scale or the flat tax.

A correction does not always mean a cash refund. If the company had a loss in a given year or income lower than the available deduction, the unused part of the relief is settled over the following six tax years. This follows from Art. 18d(8) of the CIT Act and Art. 26e(8) of the PIT Act. In such a case, the correction may improve the tax position for the future, but it does not have to result in a transfer from the tax office now.

A separate mechanism is the direct refund of the unused relief under Art. 18da of the CIT Act and Art. 26ea of the PIT Act. It applies primarily to taxpayers starting a business and, in certain cases, also to the year immediately following the year in which the business was started. This is a narrower path, subject to additional conditions, not a standard procedure for every company claiming the relief retroactively.

Finally, one more reservation is worth adding. The R&D relief does not cover ordinary, routine improvements or the standard execution of orders without a creative element and without real technical or technological uncertainty. The judgment of the Supreme Administrative Court of 20 August 2024 (II FSK 595/24) shows that in projects carried out on behalf of a client, the authorities and courts may examine not only the level of costs, but also whether R&D activity actually took place in the project. Therefore, before the correction, both the costs and the nature of the projects themselves must be assessed.

How can ALTO Advisory help?

Before a company decides on a correction, it is worth checking whether the documentation from the years to be settled will stand up to questions from the tax office. It is not enough to confirm the amount the taxpayer would like to recover. It must also be shown that the projects met the definition of R&D activity, that the costs were properly separated, and that the calculation follows from the source documents.

ALTO Advisory helps verify whether historical projects actually meet the definition of research and development activity, prepare cost records based on documents from the given period, and draft the corrected return and the application for a determination of overpayment. See how we can help your company.

FAQ: Frequently asked questions about claiming the R&D relief retroactively

Can the R&D relief be claimed retroactively?

Yes, if the given tax year is not yet time-barred and the company already met the conditions for the relief at that time. A correction does not create a new right to the relief; it only amends an earlier settlement.

How many years back can the R&D relief be claimed?

It depends on when the tax for the given year becomes time-barred, not on the date the correction is filed. In September 2026, with a standard tax year, the years 2020 and 2021, among others, can still be analysed, although 2020 in principle closes at the end of 2026.

Is a separate application needed to recover the overpayment?

Yes. Correcting the return alone is not enough. The application for a determination of overpayment must be filed together with the corrected return.

Does a correction with the R&D relief always end in an audit?

No. There is no provision requiring an audit after a correction with the R&D relief. In practice, however, the tax office may ask questions as part of verification activities or overpayment proceedings.

Does a correction always result in a cash refund?

No. If the company had a loss or too little income, the unused relief is carried forward for the next six years. If an overpayment arises, the tax office may first offset it against arrears or current tax liabilities.

Sources

• Art. 18d, 18da, 9(1b), 4a(26) to (28), 17(1)(34) and (34a) of the CIT Act (Journal of Laws 2026, item 554).
• Art. 26e, 26ea, 24a(1b), 5a(38) to (40) of the PIT Act (Journal of Laws 2026, item 592).
• Art. 70, 75, 76, 77, 78, 79, 81, 81b, 272, 274a of the Tax Ordinance Act (Journal of Laws 2026, item 622).
• General interpretation of the Minister of Finance of 13 February 2024, DD8.8203.1.2021.
• Individual interpretations of the Director of National Tax Information (KIS): 0115-KDIT3.4011.120.2026.2.PS, 0115-KDIT3.4011.831.2024.2.PS, 0114-KDIP3-2.4011.196.2022.6.MR, 0114-KDIP2-1.4010.65.2023.3.MR, 0111-KDIB1-3.4010.907.2022.3.ZK.
• Judgment of the Supreme Administrative Court of 21 March 2023, II FSK 2217/20.
• Judgment of the Supreme Administrative Court of 21 November 2024, II FSK 226/22.
• Judgment of the Supreme Administrative Court of 20 August 2024, II FSK 595/24.
• Judgment of the Provincial Administrative Court in Łódź of 17 June 2025, I SA/Łd 208/25 [non-final].

Article updated: September 2026.