Accountants foresee potential confusion in data and tax return submission deadlines due to the upcoming change in Business Activity Codes (KAD), citing errors and discrepancies that could derail this year’s filing schedule. According to the plan, the codes for approximately 1.9 million professionals and businesses will be revised in March 2026, as part of harmonization with the new European classification system. As highlighted by the Athens Accountants Association, this represents a substantial change to the tax authority’s registers, directly affecting the tax, accounting, and insurance profile of every business. The timing is considered critical, as the process coincides with the preparation and submission period for tax returns, which begins on March 16.
Accountants are sounding the alarm that the update may cause practical and substantial problems during form completion and submission. As they emphasize, the changes could create discontinuities between declared activities and the financial data of the closing fiscal year. In cases of adding or modifying business codes, additional verification is required to ensure revenues and expenses correspond to the new codes, increasing the risk of corrections and amendments.
Simultaneously, the transition to the new system may affect the completion of essential forms, such as E3 and N, since business codes are a central element for classifying activities and results. Any changes require increased attention to avoid discrepancies with data already submitted to other platforms, such as myDATA, VAT returns, and withholding taxes.
There may also be impacts on labor insurance issues, tax incentives, exemptions, or subsidies, if the change alters the company’s main business activity, potentially questioning its inclusion in specific regimes.
The Association further notes that the increased pressure of this period significantly burdens accounting firms’ workload, heightening the risk of errors or delays. In conclusion, accountants stress that updating business codes requires careful planning and close coordination with businesses to limit tax risks ahead of the filing period.
The transition steps
The tax authority has established two main phases:
– Automatic transition (1/3/2026): The mapping of old and new business codes will be carried out centrally by the tax authority during the first ten days of March.
– Review and modifications (until 1/6/2026): Businesses and professionals must check and, if necessary, correct the new codes through the myAADE platform. Note that during this same period, new registrations, changes, or business closures will not be permitted.
