Provided you’re rendering services under a specific contract over a longer period of time, your sales revenue should also be spread over this same period.

If the service is constant meaning that the content and volumes do not differ from month to month, the revenue could be equally measured to the months. That is if from March 2013 until March 2014 you’re providing a monthly service with an annual fee, each month 1/12 of the fee should be recognized to your sales revenues. 

One method of measuring those revenues is obviously also the completion method. That’s to be used if the service is done in parts and some of those parts differ from the other by the content, by volumes and so on.

A simplified means to measure revenue using the completion method is by assessing the total expenses budgeted and expenses actually incurred (in addition, if there are various phases for the contract, the assessment could be done for phases separately). The calculation made should give you a percentage, i.e. if we have budgeted expenses to be 10,000 and we’ve so far incurred 7,500 we could say that we have done 75% of the project and account 75% of the agree fee to our sales revenue.

As the name says it measures the completion and sales revenue should be recognized based on the completion level.