Entering Old Accounts with AC Code References

If your previous company accounts were filed using the old Companies House filing system or prepared with accountancy software that shows iXBRL tag codes, they may display entries with "AC" reference codes — for example, AC455 or AC30 — rather than plain English descriptions.

TinyTax uses plain English labels for all form fields. You will not see AC codes anywhere in the interface. This guide shows how to match the most common AC codes to the correct TinyTax fields.

What Are AC Codes?

AC codes come from the UK GAAP iXBRL taxonomy used by Companies House. They are technical identifiers for specific line items in company accounts.

You might see them in:

Old accounts downloaded from Companies House
Accounts prepared by accountancy software
Previous Companies House WebFiling confirmations or XML exports

Important: AC codes are not standardised across all software and filing system versions. Two accounts showing "AC455" may refer to different line items depending on which taxonomy or software produced them. If you are unsure, rely on the plain-English description next to the code in your accounts rather than the code number alone.

Balance Sheet Field Mapping (Old UK GAAP / WebFiling system)

If your accounts were produced by the old Companies House WebFiling system or older UK GAAP software, these codes apply. In this system, AC450 refers to share capital and AC30/AC50 are the asset codes.

AC Code	Description	TinyTax Field
AC30	Fixed assets (net book value)	Fixed Assets
AC50	Total current assets	Total Current Assets
AC55	Debtors	Total Current Assets (combine with AC60)
AC60	Cash at bank and in hand	Total Current Assets (combine with AC55)
AC66	Creditors: amounts due within one year	Creditors: amounts falling due within one year
AC80	Net current assets	Auto-calculated — do not enter
AC90	Total assets less current liabilities	Auto-calculated — do not enter
AC95	Creditors: amounts due after more than one year	Creditors: amounts falling due after more than one year
AC100	Provisions for liabilities	Provisions for liabilities
AC200	Net assets / shareholders' funds	Auto-calculated — do not enter
AC450	Called up share capital	Share Capital
AC455	Called up share capital not paid	Called up share capital not paid
AC490	Profit and loss account reserve	Auto-calculated from your P&L entries

Balance Sheet Field Mapping (Newer accounts / FRS 102 / FRS 105 software)

Some accountancy software and more recent accounts use a different set of AC codes where the 400-series codes refer to balance sheet assets rather than capital items. If your accounts show "AC450 = Fixed Assets" or "AC455 = Total Current Assets", use this table instead:

AC Code	Description	TinyTax Field
AC450 / AC451	Fixed assets (tangible, net book value)	Fixed Assets
AC455 / AC456	Total current assets	Total Current Assets
AC460 / AC461	Called up share capital not paid	Called up share capital not paid
AC465 / AC466	Prepayments and accrued income	Included in Total Current Assets
AC58 / AC59	Creditors: amounts falling due within one year	Creditors: amounts falling due within one year
AC60 / AC61	Net current assets	Auto-calculated — do not enter
AC62 / AC63	Total assets less current liabilities	Auto-calculated — do not enter
AC64 / AC65	Creditors: amounts falling due after more than one year	Creditors: amounts falling due after more than one year
AC66 / AC67	Provisions for liabilities	Provisions for liabilities
AC470 / AC471	Accruals and deferred income	Accruals and deferred income
AC68 / AC69	Net assets	Auto-calculated — do not enter
AC490 / AC491	Capital and reserves (total)	Auto-calculated — do not enter

In this system, odd-numbered codes are typically current year values and the next code is the prior year comparative (e.g. AC450 = current year, AC451 = prior year).

How to Enter Your Figures

Open your filing in TinyTax and scroll to the Balance Sheet section
Identify which AC code system your accounts use — check whether AC450 refers to "Fixed Assets" or "Share Capital" to determine which table to use
Match each AC code using the appropriate table above
Enter the £ value as a plain number (no £ sign, no commas)

ℹ Rows marked "Auto-calculated" — Net Current Assets, Total Assets Less Current Liabilities, Net Assets, and Capital and Reserves — are worked out automatically from the figures you enter. Leave them alone.

Share Capital does not appear as an AC code in either table because it is entered separately in TinyTax. It is the face value of shares issued to shareholders (often £1 or £100 for small companies). You will find it in the Capital and Reserves section of previous accounts, or on your confirmation statement.

TinyTax then calculates Retained Earnings automatically as: Net Assets minus Share Capital.

Common Questions

My accounts show a value for AC455 — which system is it from?

Check the description next to it. If it says "Called up share capital not paid", use the old UK GAAP table. If it says "Total current assets" or your accounts show AC450 for fixed assets, use the newer table.

I have AC codes not listed in this table

Reply to our support team with the code and value and we will identify the correct TinyTax field.

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