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<p class="lead">The technical and operational specifications of the Once-Only Technical System, laid down in the Commission’s Implementing Regulation ((EU) 2022/1463) setting out the system, are complemented by detailed, non-binding technical design documents jointly prepared by the Commission and Member States.</p>

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<p><small>Chapter 1</small></p>
<h3 class="h5">Introduction - High Level Architecture</h3>
<p>This chapter introduces the high-level architecture of the Once-Only Technical System and the key concepts and themes found in the subsequent chapters.</p>
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<p>Release date: <strong>October 2022</strong></p>
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<p><small>Chapter 2</small></p>
<h3 class="h5">User Identification, Authentication and Record Matching</h3>
<p>This chapter explains how those submitting or receiving evidences through the Once-Only Technical System are identified and authenticated.</p>
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<p>Release date: <strong>October 2022</strong></p> 
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<p><small>Chapter 3</small></p>
<h3 class="h5">Common Services</h3>
<p>This chapter looks at the Common Services (provided by the Commission) necessary for the proper execution of the evidence exchange process.</p>
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<p>Release date: <strong>October 2022</strong></p> 
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<p><small>Chapter 4</small></p>
<h3 class="h5">Evidence Exchange</h3>
<p>This chapter introduces evidence exchange in the Once-Only Technical System, which is based on bilateral data exchange between relevant authorities.</p>
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<p>Release date: <strong>October 2022</strong></p>
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<p><small>Chapter 5</small></p>
<h3 class="h5">Data Models</h3>
<p>This chapter looks at the data models that streamline the exchange of evidences, together with a methodology for defining new data models and code lists.</p>
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<p>Release date: <strong>October 2022</strong></p> 
<p><a class="btn primary" target="_blank" href="https://ec.europa.eu/digital-building-blocks/sites/x/T4YvHQ"><span>View chapter</span><span class="ico-cta"></span></a></p>
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<p><small>Chapter 6</small></p>
<h3 class="h5">OOTS Guidance & UX Recommendations</h3>
<p>This chapter provides an overview of how the Once-Only Technical System works as part of the wider Single Digital Gateway and looks at the first set of UX recommendations.</p>
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<p>Release date: <strong>October 2022</strong></p> 
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