The trial balance is normally extracted to cheek on the mathematical
accuracy of ledger entries or postings. Thus, failure of the debit and credit columns of the trial
balance to agree is an indication of the occurrence of some clerical and computational
errors such as:
1.  Transpositional Error: This is a type of error which occurs as a result
of wrong positioning  of some of the
digits in a given figure. The amount N784 
may be wrongly posted as N748, 
thereby making  one column of the
trial balance to be greater  or  smaller than the other   by 
N36(784-748). All  transpositional
errors are divisible by  9. 
2.  Slide Error: A  slide   error occurs when the  decimal points in a  particular 
figure is wrongly  placed l8
N217.50  is wrongly posted   as N21.75 . Then one side of the  trials 
balance   will be wrongly  stated by N195.75  (N217.50-2.75) . like  transpositional errors,  all slide errors are divisible  by 9
3. Placement  Errors 
:This  is a kind of error which occurs when a debit
balance is in ledger account  is
transferred to the credit side  of the
trial balance or vice versa.
4. Mathematical And Clerical Error: Such as  (i)  wrong computations in the book of original
entry  or in the ledger and (ii)  failure to 
transfer  a debit or credit balance
to the  trial balance in 
order to  locate  and of the foregoing  errors in the books   of account, the following procedures  should be followed
a.      all 
arithmetical calculations  in  the book of 
accounts should be carefully and meticulously   cross checked.
b.      Go through the ledger accounts and
ensure that, all the account balances were completely lifted to the trial
balance 
c.      Verify and ensure that all the
calculations in the books of prime entry were accurately done, and that all
postings   to the ledger were in order. 
d.      Check and see if any debit balance
was entered in the  trial balance  as a credit 
balance was entered in the trial balance as a credit balance 
e.      Obtain the difference between the
two sides of the  trial balance, if the
difference  is dividusable by  9 , then 
look out for  transposted or sided
figures. If   however, the difference is
divisible by  2,   then check 
out to see if this new figure is 
in the trial balance. 
f.       Finally,  recast the two sides of the trial balance to
ensure  it is properly added.