Accounting

Rules of Double Entry
=====================

Debit the RECEIVER
Credit the GIVER
Debit what COMES IN
Credit what GOES OUT
Debit all EXPENSES and LOSSES
Credit all INCOMES and GAINS

Invoice
==========

Debit
Credit
Receivables
150

Revenue 
100
Fright 
30
Tax 
20

Receipt
==========

Debit
Credit
Cash or Bank A/C
150

Receivables 
150

Generally these types of accounts are increased with a debit:
Dividends (Draws)
Expenses
Assets
Losses
You might think of D - E - A - L when recalling the accounts that are increased with a debit.
Generally the following types of accounts are increased with a credit:
Gains
Income
Revenues
Liabilities
Stockholders' (Owner's) Equity
You might think of G - I - R - L - S when recalling the accounts that are increased with a credit.
To decrease an account you do the opposite of what was done to increase the account. For example, an asset account is increased with a debit. Therefore it is decreased with a credit.
The abbreviation for debit is dr. and the abbreviation for credit is cr.

Receivable Accounting Entries
Standard Invoice
Dr Receivables—Trade A/c
Cr Revenue

Receipt
Dr Cash
Cr Receivables

Payable Accounting entries 

Invoice
Dr.Expense A/c
Cr.Liablity A/c

Payment
Dr.Liablity
Cr.Cash

Invoicing Rule  In Advance
Dr.Receivables
Cr.Unearned Revenue

After Revenue Recognition
Dr Unearned Revenue
Cr Revenue

Invoicing Rule  In Arrears 
Dr Unbilled Receivable
Cr Revenue
Receivable account will be recognized at the end of revenue recognition.
Dr Receivable
Cr Unbilled Receivable

Deposit Invoice
Dr Receivables—Deposit A/c
Cr Revenue