Errors of Commission: When a transaction has been mis-recorded either wholly or partially it is called as a error of commission. Error of commission can happen in the following ways-

(i) Errors in posting:

These are the most common forms of error of commissions. Posting errors may be of a wrong account, wrong amount or wrong file. Here are some examples:

a. An amount of Rs 360 was received from Mr. Ram, but Mr. Shyam's account was credited in the books.

b. Goods purchased from Mr. P for Rs 729 recorded in the books at Rs. 279.

c. Sales returns from Mr X posted on the debit side of his account.

The first type of errors will not affect the trial balance, however, the other two will affect the agreement of trial balance.

(ii) Errors in Casting:

Casting errors are the errors committed while making the totals. This error affects the trial Balance.

(iii) Errors in carrying forward and extraction of balances:

Error of carry forward and errors of extraction of balances also affect the trial balance.

(iv) Errors of duplication:

Error of duplication is another type of error of commission which means recording the same transaction twice. Such errors however, do not affect the trial balance but they will affect the Statement of Profit and Loss (over statement of expenditure).