GPT-5.3-Codex vs Kimi K3 for bookkeeping

You have an **unexplained difference of £36.00**:

\[
£8,412.55 - £8,376.55 = £36.00
\]

The £120 unpresented cheque and £120 lodgement cancel out, so they are **not** the cause.

### What kind of error this is
This is the classic pattern of a **transposition error** (digits swapped), e.g. **£451** vs **£415**.

\[
451 - 415 = 36
\]

### The quick arithmetic rule
If a reconciliation difference is divisible by **9**, suspect a transposition or similar digit error.

\[
36 \div 9 = 4 \text{ exactly}
\]

So £36 immediately points to that class of e…

### 1. Difference

\[
£8,412.55-£8,376.55=\boxed{£36.00}
\]

The unpresented cheque and outstanding lodgement cancel:

\[
£8,412.55-£120+£120=£8,412.55
\]

So the unexplained difference remains **£36, with the bank balance higher than the cash book**.

### 2. Type of error indicated

£36 has the classic signature of a **digit-transposition error**:

\[
£451-£415=£36
\]

The rule is that a difference caused by transposing digits is divisible by 9:

\[
36\div 9=4
\]

For adjacent digits \(a\) and \(b\):

\[
(10a+b)-(10b+a)=9(a-b)
\]

More general…