Overview
HM Revenue & Customs released updated Inheritance Tax forms in December 2025, affecting the IHT400, IHT401a, and IHT417 documents used in probate matters.
These changes introduce new questions, additional data fields, and expanded reporting requirements.
Firms using Proclaim's Probate case type should apply system updates to ensure compliance with the new HMRC form requirements.
Note : The IHT401a screens were introduced in April 2025 so may not be available in all systems.
What's Changed?
IHT400
Q13a: New deceased nationality field
Q48c: New double taxation domicile question
IHT401a
Q1a: New double taxation convention question
Q4: New country of residence fields for tax details (20 entries)
Q6: Expansion of tax residence history from 19 to 20 years, with country fields
IHT417
Q11: New foreign will distribution question and country identification field
Who Needs to Take Action?
System Administrators with:
Administrator-level access to Proclaim system development tools
Technical Level 1 training or equivalent experience in Proclaim configuration
Access to Database Maintenance, Screen Designer, Option Maintenance, and Workflow Maintenance programs
Download the Updated Forms
The amended forms are now available for download from the Access Customer Success Portal.
Implementation Guide
Comprehensive step-by-step implementation instructions are provided in the attached release notes document. The guide covers:
Database Maintenance: Creating new fields (Alpha and Option types)
Screen Designer: Adding fields to screens and updating layouts
Option Maintenance: Populating option field entries
Workflow Maintenance: Updating Send Letter templates and amending Linked Actions
Each form update is documented separately with detailed instructions, including:
Field specifications and table assignments
Screen layout modifications
Complex maths routine updates for table manipulation
Document template field mapping
Important Notes
Prerequisites:
Back up the existing Linked Actions before making any changes
Ensure you have completed Technical Level 1 training or equivalent
Contact Access Legal Support if uncertain about any updates
IHT401a Specific: The screens for IHT401a were added to Proclaim in April 2025 and may not be present in all systems. If these screens are not in your system, you can skip the IHT401a updates.
Timeline: These updates should be implemented as soon as practically possible to ensure all new Inheritance Tax form submissions meet current HMRC standards.
Technical Complexity
The updates involve:
Creating new database fields across three forms
Modifying screens
Updating Linked Actions with complex table manipulation logic
Adding fields to multiple document templates