Company MTD Mapping (CT600)

This page explains how Trade Control presents company account mappings for the MTD CT600 interface.

It is written for technical implementers and advanced users who need a clear understanding of how company accounts are surfaced, grouped, and validated for the first micro-accounts release.

The focus is on the MTD interface, not the internal template tree. Where the Category Tree is referenced, it is only to explain how a mapping resolves.

Abridged and full account formats will be added in later releases.

Company mapping process - how Trade Control builds the company MTD CT600 micro-accounts mapping from template definitions and live transactions

Scope

In scope:

MTD CT600 company mapping interface
Micro-accounts only
Canonical reporting groups
AC-code mapping model
How mappings resolve into the Category Tree
Template behaviour (BASE, MICRO_CUR, MICRO_CUR_STD) where relevant
Validation and configuration notes

Out of scope:

Abridged or full statutory accounts
Detailed template internals
Non-MTD reporting formats
Future account formats not included in the first release

1. Overview of the MTD Company Mapping Interface

The Company MTD interface provides a single, consolidated view of how a business’s financial activity is mapped into the CT600 reporting structure.

The interface presents:

Canonical reporting groups such as Turnover, Other Income, and Direct Costs
AC-codes used by HMRC for CT600 micro-entity submissions
Totals derived from the Category Tree
Validation indicators for missing or inconsistent mappings

The user does not interact with the Category Tree directly.

Instead, the interface shows reporting totals, each backed by a deterministic mapping chain:

AC-code → Reporting Group → Category → Cash Codes → Transactions

This page explains how that chain works.

2. Canonical Reporting Groups

The micro-accounts CT600 format uses a small, stable set of reporting groups.

These appear directly in the MTD interface.

Reporting Group	Description
Turnover	Sales income from normal trading activity
Other Income	Non-trading income, for example grants or sundry income
Direct Costs	Costs directly attributable to generating turnover
Staff Costs	Wages, salaries, subcontractors, and related staff cost headings
Admin Costs	General administrative overheads
Premises Costs	Rent, heat, light, and repairs
Depreciation	Depreciation charges for plant, vehicles, and fixtures
Tax	Corporation tax charge
Profit	Profit before tax or after tax, as required by CT600 micro
Capital / Balance Sheet	Equipment, adjustments, share capital, and reserves

These groups are populated automatically using the mapping model described next.

3. AC-Codes Used in Micro-Accounts

The following AC-codes are used by the micro-entity CT600 format and are supported by the MTD interface.

AC Code	Description	Source
`AC12`	Turnover	`MICRO_CUR_2026`
`AC405`	Other income	`MICRO_CUR_2026`
`AC410`	Direct costs	`MICRO_CUR_2026`
`AC415`	Staff costs	`MICRO_CUR_2026`
`AC420`	Depreciation	`MICRO_CUR_2026` / STD override
`AC425`	Other charges / admin	`MICRO_CUR_2026`
`AC34`	Profit or loss	`MICRO_CUR_2026`
`AC435`	Tax on profit	`MICRO_CUR_2026`
`CP28`	Additions to equipment	`MICRO_CUR_STD_2026`
`CP46`	Depreciation adjustments	`MICRO_CUR_STD_2026`

These codes are surfaced directly in the MTD interface.

The mapping logic behind them is described below.

4. Mapping Model

The MTD interface uses a deterministic mapping chain:

AC-code → Category → Cash Codes → Transactions

4.1 AC-code assignment

Each AC-code is mapped to a Category in the template layer:

BASE_MIN_2026 defines the foundational categories
MICRO_CUR_2026 assigns AC-codes to those categories
MICRO_CUR_STD_2026 refines or overrides mappings, for example depreciation splits

4.2 Category → Cash Code resolution

Each Category contains one or more cash codes.

These represent the operational buckets used by the business.

Examples:

CA-SALES → CC-SALES
CA-SALES → CC-SALAB
CA-SALES → CC-SAMAT
CA-DIRECT → CC-MAT
CA-DIRECT → CC-SUB
CA-DIRECT → CC-FUEL
CA-DIRECT → CC-MTRAV
CA-ASSET → CC-DEPRC
CA-ASSET → CC-DEPRJ
CA-ASSET → CC-DEPPL
CA-ASSET → CC-DEPMV
CA-ASSET → CC-DEPFX

4.3 Cash Code → Transaction totals

At runtime, the system totals all transactions assigned to the cash codes for a category.

These totals feed the AC-code values shown in the MTD interface.

4.4 Template stack behaviour

The template stack is additive:

BASE_MIN_2026

Defines the core company tree, including sales, direct costs, staff, admin, premises, depreciation, tax, and capital
Creates the foundational cash codes and assigns them to those categories
Provides the minimum depreciation and tax structure used by the micro accounts release

MICRO_CUR_2026

Adds the micro-accounts AC-codes
Maps the reporting groups and categories to those AC-codes
Provides the first complete micro-entity reporting surface for the MTD interface

MICRO_CUR_STD_2026

Adds more granular cash codes for materials, subcontractors, building, and admin
Splits depreciation into plant, vehicles, and fixtures
Adds CP28 and CP46 mappings
Overrides BASE depreciation behaviour so the STD definitions drive the final totals

The MTD interface always reflects the final resolved mapping after all template layers are applied.

5. Micro-Accounts Release

The first release supports:

Micro-entity CT600 format
Full AC-code mapping for micro accounts
Standardised reporting groups
Deterministic mapping from template to MTD interface
Automatic validation of missing or unmapped categories

Not included:

Abridged accounts
Full accounts
Director disclosures
Notes to the accounts
Multi-format switching

These will be added in later releases.

6. How the Category Tree Fits In

The Category Tree is the internal semantic model used by the platform.

It is not shown directly in the MTD interface.

The tree provides:

Category definitions
Cash code membership
Roll-ups
Expression categories for profit, tax, and depreciation
Capital account structure

The MTD interface consumes totals, not the tree itself.

You only need to reference the Category Tree when:

diagnosing a missing total
understanding why a value appears under a specific AC-code
validating template overrides
extending the template for custom deployments

7. Validation and Configuration Notes

The MTD interface performs several checks:

Unmapped categories
Categories without AC-codes are flagged.
Zero-value categories
Shown but not flagged; useful for diagnostics.
Unexpected totals
Indicates a cash code assigned to the wrong category.
Depreciation override checks
Ensures STD depreciation replaces BASE depreciation cleanly.
Capital account consistency
Ensures CP28 and CP46 totals match equipment movements.

For implementers, the most common issues arise from:

custom cash codes not assigned to categories
category overrides that break roll-ups
missing STD depreciation splits